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	$81.88	13.500%	$92.9338	$92.93	$92.95	$92.90
Purchase #2	$248.72	11.160%	$276.4772	$276.48	$276.50	$276.50
Purchase #3	$191.54	9.397%	$209.539	$209.54	$209.55	$209.50
Purchase #4	$134.85	12.641%	$151.8964	$151.90	$151.90	$151.90
Purchase #5	$109.83	6.191%	$116.6296	$116.63	$116.65	$116.60
Purchase #6	$126.74	11.423%	$141.2175	$141.22	$141.20	$141.20
Purchase #7	$188.96	5.633%	$199.6041	$199.60	$199.60	$199.60
7 purchase totals =	$1,082.52		$1,188.2976	$1,188.30	$1,188.35	$1,188.20