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	$126.29	12.387%	$141.9335	$141.93	$141.95	$141.90
Purchase #2	$167.49	4.284%	$174.6653	$174.67	$174.65	$174.70
Purchase #3	$62.38	8.470%	$67.6636	$67.66	$67.65	$67.70
Purchase #4	$128.61	8.501%	$139.5431	$139.54	$139.55	$139.50
Purchase #5	$51.52	3.717%	$53.435	$53.44	$53.45	$53.40
Purchase #6	$185.34	11.227%	$206.1481	$206.15	$206.15	$206.10
Purchase #7	$38.62	6.539%	$41.1454	$41.15	$41.15	$41.10
7 purchase totals =	$760.25		$824.5340	$824.54	$824.55	$824.40