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	$50.45	6.295%	$53.6258	$53.63	$53.65	$53.60
Purchase #2	$27.51	9.564%	$30.1411	$30.14	$30.15	$30.10
Purchase #3	$203.42	9.309%	$222.3564	$222.36	$222.35	$222.40
Purchase #4	$240.65	11.803%	$269.0539	$269.05	$269.05	$269.10
Purchase #5	$131.70	3.606%	$136.4491	$136.45	$136.45	$136.40
Purchase #6	$74.89	10.137%	$82.4816	$82.48	$82.50	$82.50
Purchase #7	$55.83	3.511%	$57.7902	$57.79	$57.80	$57.80
7 purchase totals =	$784.45		$851.8981	$851.90	$851.95	$851.90