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	$143.88	4.776%	$150.7517	$150.75	$150.75	$150.80
Purchase #2	$189.72	4.114%	$197.5251	$197.53	$197.55	$197.50
Purchase #3	$145.81	9.488%	$159.6445	$159.64	$159.65	$159.60
Purchase #4	$211.83	3.533%	$219.314	$219.31	$219.30	$219.30
Purchase #5	$165.52	3.563%	$171.4175	$171.42	$171.40	$171.40
Purchase #6	$81.88	12.617%	$92.2108	$92.21	$92.20	$92.20
Purchase #7	$124.89	13.264%	$141.4554	$141.46	$141.45	$141.50
7 purchase totals =	$1,063.53		$1,132.3190	$1,132.32	$1,132.30	$1,132.30