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	$223.70	12.126%	$250.8259	$250.83	$250.85	$250.80
Purchase #2	$117.63	11.315%	$130.9398	$130.94	$130.95	$130.90
Purchase #3	$27.90	5.127%	$29.3304	$29.33	$29.35	$29.30
Purchase #4	$85.27	7.774%	$91.8989	$91.90	$91.90	$91.90
Purchase #5	$148.30	12.447%	$166.7589	$166.76	$166.75	$166.80
Purchase #6	$178.31	7.394%	$191.4942	$191.49	$191.50	$191.50
Purchase #7	$136.69	13.550%	$155.2115	$155.21	$155.20	$155.20
7 purchase totals =	$917.80		$1,016.4596	$1,016.46	$1,016.50	$1,016.40