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	$185.53	8.663%	$201.6025	$201.60	$201.60	$201.60
Purchase #2	$192.47	8.201%	$208.2545	$208.25	$208.25	$208.30
Purchase #3	$73.60	6.819%	$78.6188	$78.62	$78.60	$78.60
Purchase #4	$172.44	10.196%	$190.022	$190.02	$190.00	$190.00
Purchase #5	$113.27	12.604%	$127.5466	$127.55	$127.55	$127.50
Purchase #6	$57.50	11.344%	$64.0228	$64.02	$64.00	$64.00
Purchase #7	$205.41	7.326%	$220.4583	$220.46	$220.45	$220.50
7 purchase totals =	$1,000.22		$1,090.5255	$1,090.52	$1,090.45	$1,090.50