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	$53.25	6.346%	$56.6292	$56.63	$56.65	$56.60
Purchase #2	$66.83	7.340%	$71.7353	$71.74	$71.75	$71.70
Purchase #3	$241.89	6.715%	$258.1329	$258.13	$258.15	$258.10
Purchase #4	$201.31	11.264%	$223.9856	$223.99	$224.00	$224.00
Purchase #5	$230.41	4.712%	$241.2669	$241.27	$241.25	$241.30
Purchase #6	$222.56	12.483%	$250.3422	$250.34	$250.35	$250.30
Purchase #7	$115.48	10.551%	$127.6643	$127.66	$127.65	$127.70
7 purchase totals =	$1,131.73		$1,229.7564	$1,229.76	$1,229.80	$1,229.70