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	$238.44	11.483%	$265.8201	$265.82	$265.80	$265.80
Purchase #2	$58.58	11.370%	$65.2405	$65.24	$65.25	$65.20
Purchase #3	$233.52	7.791%	$251.7135	$251.71	$251.70	$251.70
Purchase #4	$222.30	9.581%	$243.5986	$243.60	$243.60	$243.60
Purchase #5	$137.96	10.295%	$152.163	$152.16	$152.15	$152.20
Purchase #6	$166.72	7.315%	$178.9156	$178.92	$178.90	$178.90
Purchase #7	$221.31	9.424%	$242.1663	$242.17	$242.15	$242.20
7 purchase totals =	$1,278.83		$1,399.6176	$1,399.62	$1,399.55	$1,399.60