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	$131.70	12.801%	$148.5589	$148.56	$148.55	$148.60
Purchase #2	$167.28	10.169%	$184.2907	$184.29	$184.30	$184.30
Purchase #3	$202.70	9.529%	$222.0153	$222.02	$222.00	$222.00
Purchase #4	$111.45	8.436%	$120.8519	$120.85	$120.85	$120.90
Purchase #5	$245.50	7.840%	$264.7472	$264.75	$264.75	$264.70
Purchase #6	$201.46	13.432%	$228.5201	$228.52	$228.50	$228.50
Purchase #7	$47.63	6.120%	$50.545	$50.55	$50.55	$50.50
7 purchase totals =	$1,107.72		$1,219.5291	$1,219.54	$1,219.50	$1,219.50