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	$142.97	6.587%	$152.3874	$152.39	$152.40	$152.40
Purchase #2	$62.64	13.837%	$71.3075	$71.31	$71.30	$71.30
Purchase #3	$225.83	6.538%	$240.5948	$240.59	$240.60	$240.60
Purchase #4	$218.69	11.799%	$244.4932	$244.49	$244.50	$244.50
Purchase #5	$88.26	3.289%	$91.1629	$91.16	$91.15	$91.20
Purchase #6	$107.80	5.853%	$114.1095	$114.11	$114.10	$114.10
Purchase #7	$7.70	10.707%	$8.5244	$8.52	$8.50	$8.50
7 purchase totals =	$853.89		$922.5797	$922.57	$922.55	$922.60