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	$44.66	10.454%	$49.3288	$49.33	$49.35	$49.30
Purchase #2	$193.36	9.149%	$211.0505	$211.05	$211.05	$211.10
Purchase #3	$69.85	12.746%	$78.7531	$78.75	$78.75	$78.80
Purchase #4	$203.81	9.355%	$222.8764	$222.88	$222.90	$222.90
Purchase #5	$74.98	4.380%	$78.2641	$78.26	$78.25	$78.30
Purchase #6	$118.54	6.821%	$126.6256	$126.63	$126.65	$126.60
Purchase #7	$83.40	7.570%	$89.7134	$89.71	$89.70	$89.70
7 purchase totals =	$788.60		$856.6119	$856.61	$856.65	$856.70