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	$158.62	8.366%	$171.8901	$171.89	$171.90	$171.90
Purchase #2	$127.34	4.827%	$133.4867	$133.49	$133.50	$133.50
Purchase #3	$195.56	8.298%	$211.7876	$211.79	$211.80	$211.80
Purchase #4	$68.29	6.112%	$72.4639	$72.46	$72.45	$72.50
Purchase #5	$160.35	4.109%	$166.9388	$166.94	$166.95	$166.90
Purchase #6	$19.59	9.519%	$21.4548	$21.45	$21.45	$21.50
Purchase #7	$222.83	13.689%	$253.3332	$253.33	$253.35	$253.30
7 purchase totals =	$952.58		$1,031.3551	$1,031.35	$1,031.40	$1,031.40