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	$61.86	4.454%	$64.6152	$64.62	$64.60	$64.60
Purchase #2	$176.35	8.278%	$190.9483	$190.95	$190.95	$190.90
Purchase #3	$91.50	10.208%	$100.8403	$100.84	$100.85	$100.80
Purchase #4	$26.74	5.738%	$28.2743	$28.27	$28.25	$28.30
Purchase #5	$222.94	9.236%	$243.5307	$243.53	$243.55	$243.50
Purchase #6	$174.27	7.259%	$186.9203	$186.92	$186.90	$186.90
Purchase #7	$211.51	7.469%	$227.3077	$227.31	$227.30	$227.30
7 purchase totals =	$965.17		$1,042.4368	$1,042.44	$1,042.40	$1,042.30