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	$190.69	9.775%	$209.3299	$209.33	$209.35	$209.30
Purchase #2	$222.70	6.279%	$236.6833	$236.68	$236.70	$236.70
Purchase #3	$66.72	7.278%	$71.5759	$71.58	$71.60	$71.60
Purchase #4	$137.58	6.340%	$146.3026	$146.30	$146.30	$146.30
Purchase #5	$154.28	11.336%	$171.7692	$171.77	$171.75	$171.80
Purchase #6	$218.40	13.511%	$247.908	$247.91	$247.90	$247.90
Purchase #7	$92.96	13.838%	$105.8238	$105.82	$105.80	$105.80
7 purchase totals =	$1,083.33		$1,189.3927	$1,189.39	$1,189.40	$1,189.40