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	$182.58	7.434%	$196.153	$196.15	$196.15	$196.20
Purchase #2	$158.37	12.653%	$178.4086	$178.41	$178.40	$178.40
Purchase #3	$166.91	4.737%	$174.8165	$174.82	$174.80	$174.80
Purchase #4	$189.50	10.650%	$209.6818	$209.68	$209.70	$209.70
Purchase #5	$53.63	3.604%	$55.5628	$55.56	$55.55	$55.60
Purchase #6	$114.93	7.336%	$123.3613	$123.36	$123.35	$123.40
Purchase #7	$85.75	13.840%	$97.6178	$97.62	$97.60	$97.60
7 purchase totals =	$951.67		$1,035.6018	$1,035.60	$1,035.55	$1,035.70