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	$113.70	6.372%	$120.945	$120.95	$120.95	$120.90
Purchase #2	$19.71	9.679%	$21.6177	$21.62	$21.60	$21.60
Purchase #3	$188.37	6.488%	$200.5914	$200.59	$200.60	$200.60
Purchase #4	$54.53	7.645%	$58.6988	$58.70	$58.70	$58.70
Purchase #5	$30.32	11.253%	$33.7319	$33.73	$33.75	$33.70
Purchase #6	$47.73	5.600%	$50.4029	$50.40	$50.40	$50.40
Purchase #7	$166.86	11.244%	$185.6217	$185.62	$185.60	$185.60
7 purchase totals =	$621.22		$671.6094	$671.61	$671.60	$671.50