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	$195.69	13.439%	$221.9888	$221.99	$222.00	$222.00
Purchase #2	$81.80	12.809%	$92.2778	$92.28	$92.30	$92.30
Purchase #3	$65.45	10.825%	$72.535	$72.54	$72.55	$72.50
Purchase #4	$93.55	12.256%	$105.0155	$105.02	$105.00	$105.00
Purchase #5	$169.48	12.730%	$191.0548	$191.05	$191.05	$191.10
Purchase #6	$235.36	7.629%	$253.3156	$253.32	$253.30	$253.30
Purchase #7	$140.52	7.796%	$151.4749	$151.47	$151.45	$151.50
7 purchase totals =	$981.85		$1,087.6624	$1,087.67	$1,087.65	$1,087.70