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	$173.45	10.228%	$191.1905	$191.19	$191.20	$191.20
Purchase #2	$170.64	12.191%	$191.4427	$191.44	$191.45	$191.40
Purchase #3	$111.57	4.455%	$116.5404	$116.54	$116.55	$116.50
Purchase #4	$42.88	6.186%	$45.5326	$45.53	$45.55	$45.50
Purchase #5	$104.62	10.817%	$115.9367	$115.94	$115.95	$115.90
Purchase #6	$219.88	8.266%	$238.0553	$238.06	$238.05	$238.10
Purchase #7	$125.52	11.790%	$140.3188	$140.32	$140.30	$140.30
7 purchase totals =	$948.56		$1,039.0170	$1,039.02	$1,039.05	$1,038.90