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	$70.64	9.472%	$77.331	$77.33	$77.35	$77.30
Purchase #2	$199.77	11.343%	$222.4299	$222.43	$222.45	$222.40
Purchase #3	$168.72	9.127%	$184.1191	$184.12	$184.10	$184.10
Purchase #4	$211.61	5.782%	$223.8453	$223.85	$223.85	$223.80
Purchase #5	$179.66	7.871%	$193.801	$193.80	$193.80	$193.80
Purchase #6	$222.25	7.322%	$238.5231	$238.52	$238.50	$238.50
Purchase #7	$198.93	8.315%	$215.471	$215.47	$215.45	$215.50
7 purchase totals =	$1,251.58		$1,355.5204	$1,355.52	$1,355.50	$1,355.40