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	$54.85	11.690%	$61.262	$61.26	$61.25	$61.30
Purchase #2	$223.77	7.429%	$240.3939	$240.39	$240.40	$240.40
Purchase #3	$122.29	4.574%	$127.8835	$127.88	$127.90	$127.90
Purchase #4	$220.92	13.223%	$250.1323	$250.13	$250.15	$250.10
Purchase #5	$150.94	11.207%	$167.8558	$167.86	$167.85	$167.90
Purchase #6	$194.80	12.536%	$219.2201	$219.22	$219.20	$219.20
Purchase #7	$68.43	5.512%	$72.2019	$72.20	$72.20	$72.20
7 purchase totals =	$1,036.00		$1,138.9495	$1,138.94	$1,138.95	$1,139.00