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	$149.73	10.130%	$164.8976	$164.90	$164.90	$164.90
Purchase #2	$60.55	6.227%	$64.3204	$64.32	$64.30	$64.30
Purchase #3	$234.54	5.707%	$247.9252	$247.93	$247.95	$247.90
Purchase #4	$153.33	8.853%	$166.9043	$166.90	$166.90	$166.90
Purchase #5	$48.27	12.771%	$54.4346	$54.43	$54.45	$54.40
Purchase #6	$85.98	7.197%	$92.168	$92.17	$92.15	$92.20
Purchase #7	$185.53	13.242%	$210.0979	$210.10	$210.10	$210.10
7 purchase totals =	$917.93		$1,000.7480	$1,000.75	$1,000.75	$1,000.70