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	$46.28	13.103%	$52.3441	$52.34	$52.35	$52.30
Purchase #2	$165.25	3.831%	$171.5807	$171.58	$171.60	$171.60
Purchase #3	$5.84	13.106%	$6.6054	$6.61	$6.60	$6.60
Purchase #4	$130.69	7.841%	$140.9374	$140.94	$140.95	$140.90
Purchase #5	$220.37	10.239%	$242.9337	$242.93	$242.95	$242.90
Purchase #6	$241.76	3.532%	$250.299	$250.30	$250.30	$250.30
Purchase #7	$191.42	10.369%	$211.2683	$211.27	$211.25	$211.30
7 purchase totals =	$1,001.61		$1,075.9686	$1,075.97	$1,076.00	$1,075.90