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	$173.52	5.364%	$182.8276	$182.83	$182.85	$182.80
Purchase #2	$115.50	13.631%	$131.2438	$131.24	$131.25	$131.20
Purchase #3	$231.65	6.787%	$247.3721	$247.37	$247.35	$247.40
Purchase #4	$216.36	10.263%	$238.565	$238.57	$238.55	$238.60
Purchase #5	$72.83	8.102%	$78.7307	$78.73	$78.75	$78.70
Purchase #6	$79.84	11.549%	$89.0607	$89.06	$89.05	$89.10
Purchase #7	$139.70	12.494%	$157.1541	$157.15	$157.15	$157.20
7 purchase totals =	$1,029.40		$1,124.9540	$1,124.95	$1,124.95	$1,125.00