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	$171.73	12.346%	$192.9318	$192.93	$192.95	$192.90
Purchase #2	$108.51	7.309%	$116.441	$116.44	$116.45	$116.40
Purchase #3	$19.82	9.427%	$21.6884	$21.69	$21.70	$21.70
Purchase #4	$59.92	4.774%	$62.7806	$62.78	$62.80	$62.80
Purchase #5	$129.64	10.121%	$142.7609	$142.76	$142.75	$142.80
Purchase #6	$48.89	11.830%	$54.6737	$54.67	$54.65	$54.70
Purchase #7	$57.32	6.599%	$61.1025	$61.10	$61.10	$61.10
7 purchase totals =	$595.83		$652.3789	$652.37	$652.40	$652.40