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	$176.39	11.573%	$196.8036	$196.80	$196.80	$196.80
Purchase #2	$84.26	9.677%	$92.4138	$92.41	$92.40	$92.40
Purchase #3	$221.59	7.471%	$238.145	$238.15	$238.15	$238.10
Purchase #4	$95.28	10.690%	$105.4654	$105.47	$105.45	$105.50
Purchase #5	$172.39	10.274%	$190.1013	$190.10	$190.10	$190.10
Purchase #6	$85.83	3.530%	$88.8598	$88.86	$88.85	$88.90
Purchase #7	$17.67	8.764%	$19.2186	$19.22	$19.20	$19.20
7 purchase totals =	$853.41		$931.0075	$931.01	$930.95	$931.00