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	$110.54	3.542%	$114.4553	$114.46	$114.45	$114.50
Purchase #2	$99.41	12.229%	$111.5668	$111.57	$111.55	$111.60
Purchase #3	$219.97	3.872%	$228.4872	$228.49	$228.50	$228.50
Purchase #4	$32.60	8.810%	$35.4721	$35.47	$35.45	$35.50
Purchase #5	$186.97	4.121%	$194.675	$194.68	$194.70	$194.70
Purchase #6	$146.32	4.454%	$152.8371	$152.84	$152.85	$152.80
Purchase #7	$234.48	11.773%	$262.0853	$262.09	$262.10	$262.10
7 purchase totals =	$1,030.29		$1,099.5788	$1,099.60	$1,099.60	$1,099.70