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	$168.51	12.817%	$190.1079	$190.11	$190.10	$190.10
Purchase #2	$38.50	10.194%	$42.4247	$42.42	$42.40	$42.40
Purchase #3	$249.68	10.369%	$275.5693	$275.57	$275.55	$275.60
Purchase #4	$11.33	6.599%	$12.0777	$12.08	$12.10	$12.10
Purchase #5	$155.86	13.418%	$176.7733	$176.77	$176.75	$176.80
Purchase #6	$80.79	13.354%	$91.5787	$91.58	$91.60	$91.60
Purchase #7	$206.63	12.807%	$233.0931	$233.09	$233.10	$233.10
7 purchase totals =	$911.30		$1,021.6247	$1,021.62	$1,021.60	$1,021.70