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	$136.68	9.834%	$150.1211	$150.12	$150.10	$150.10
Purchase #2	$144.59	3.755%	$150.0194	$150.02	$150.00	$150.00
Purchase #3	$47.29	4.316%	$49.331	$49.33	$49.35	$49.30
Purchase #4	$42.93	12.738%	$48.3984	$48.40	$48.40	$48.40
Purchase #5	$203.54	4.513%	$212.7258	$212.73	$212.75	$212.70
Purchase #6	$31.69	5.787%	$33.5239	$33.52	$33.50	$33.50
Purchase #7	$219.63	6.494%	$233.8928	$233.89	$233.90	$233.90
7 purchase totals =	$826.35		$878.0124	$878.01	$878.00	$877.90