Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.65	8.839%	$191.1757	$191.18	$191.20	$191.20
Purchase #2	$202.43	5.275%	$213.1082	$213.11	$213.10	$213.10
Purchase #3	$147.69	5.744%	$156.1733	$156.17	$156.15	$156.20
Purchase #4	$157.44	13.507%	$178.7054	$178.71	$178.70	$178.70
Purchase #5	$118.84	10.732%	$131.5939	$131.59	$131.60	$131.60
Purchase #6	$228.90	6.212%	$243.1193	$243.12	$243.10	$243.10
Purchase #7	$108.77	13.548%	$123.5062	$123.51	$123.50	$123.50
7 purchase totals =	$1,139.72		$1,237.3820	$1,237.39	$1,237.35	$1,237.40