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	$54.75	11.565%	$61.0818	$61.08	$61.10	$61.10
Purchase #2	$159.65	6.703%	$170.3513	$170.35	$170.35	$170.40
Purchase #3	$213.83	7.339%	$229.523	$229.52	$229.50	$229.50
Purchase #4	$152.83	7.115%	$163.7039	$163.70	$163.70	$163.70
Purchase #5	$173.91	13.130%	$196.7444	$196.74	$196.75	$196.70
Purchase #6	$101.81	7.593%	$109.5404	$109.54	$109.55	$109.50
Purchase #7	$134.69	11.625%	$150.3477	$150.35	$150.35	$150.30
7 purchase totals =	$991.47		$1,081.2925	$1,081.28	$1,081.30	$1,081.20