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	$189.89	11.463%	$211.6571	$211.66	$211.65	$211.70
Purchase #2	$226.34	7.664%	$243.6867	$243.69	$243.70	$243.70
Purchase #3	$33.64	6.828%	$35.9369	$35.94	$35.95	$35.90
Purchase #4	$128.56	11.769%	$143.6902	$143.69	$143.70	$143.70
Purchase #5	$238.80	4.496%	$249.5364	$249.54	$249.55	$249.50
Purchase #6	$147.27	10.185%	$162.2694	$162.27	$162.25	$162.30
Purchase #7	$9.32	11.103%	$10.3548	$10.35	$10.35	$10.40
7 purchase totals =	$973.82		$1,057.1315	$1,057.14	$1,057.15	$1,057.20