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	$215.35	3.473%	$222.8291	$222.83	$222.85	$222.80
Purchase #2	$234.37	9.261%	$256.075	$256.08	$256.10	$256.10
Purchase #3	$58.76	12.589%	$66.1573	$66.16	$66.15	$66.20
Purchase #4	$236.61	8.164%	$255.9268	$255.93	$255.95	$255.90
Purchase #5	$103.34	11.573%	$115.2995	$115.30	$115.30	$115.30
Purchase #6	$145.83	3.352%	$150.7182	$150.72	$150.70	$150.70
Purchase #7	$81.42	8.454%	$88.3032	$88.30	$88.30	$88.30
7 purchase totals =	$1,075.68		$1,155.3091	$1,155.32	$1,155.35	$1,155.30