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	$55.76	10.737%	$61.747	$61.75	$61.75	$61.70
Purchase #2	$239.59	10.255%	$264.16	$264.16	$264.15	$264.20
Purchase #3	$37.71	8.360%	$40.8626	$40.86	$40.85	$40.90
Purchase #4	$26.70	3.137%	$27.5376	$27.54	$27.55	$27.50
Purchase #5	$141.98	9.753%	$155.8273	$155.83	$155.85	$155.80
Purchase #6	$133.84	13.667%	$152.1319	$152.13	$152.15	$152.10
Purchase #7	$52.35	7.455%	$56.2527	$56.25	$56.25	$56.30
7 purchase totals =	$687.93		$758.5191	$758.52	$758.55	$758.50