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	$239.62	12.306%	$269.1076	$269.11	$269.10	$269.10
Purchase #2	$196.64	9.169%	$214.6699	$214.67	$214.65	$214.70
Purchase #3	$56.58	5.146%	$59.4916	$59.49	$59.50	$59.50
Purchase #4	$156.60	3.165%	$161.5564	$161.56	$161.55	$161.60
Purchase #5	$55.69	6.842%	$59.5003	$59.50	$59.50	$59.50
Purchase #6	$138.33	8.670%	$150.3232	$150.32	$150.30	$150.30
Purchase #7	$167.84	3.499%	$173.7127	$173.71	$173.70	$173.70
7 purchase totals =	$1,011.30		$1,088.3617	$1,088.36	$1,088.30	$1,088.40