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	$68.34	3.767%	$70.9144	$70.91	$70.90	$70.90
Purchase #2	$174.89	9.551%	$191.5937	$191.59	$191.60	$191.60
Purchase #3	$152.48	9.170%	$166.4624	$166.46	$166.45	$166.50
Purchase #4	$83.91	8.574%	$91.1044	$91.10	$91.10	$91.10
Purchase #5	$137.29	10.165%	$151.2455	$151.25	$151.25	$151.20
Purchase #6	$236.36	3.160%	$243.829	$243.83	$243.85	$243.80
Purchase #7	$205.37	12.191%	$230.4067	$230.41	$230.40	$230.40
7 purchase totals =	$1,058.64		$1,145.5561	$1,145.55	$1,145.55	$1,145.50