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	$162.75	10.725%	$180.2049	$180.20	$180.20	$180.20
Purchase #2	$191.78	11.599%	$214.0246	$214.02	$214.00	$214.00
Purchase #3	$184.86	11.581%	$206.2686	$206.27	$206.25	$206.30
Purchase #4	$100.63	13.177%	$113.89	$113.89	$113.90	$113.90
Purchase #5	$157.28	6.250%	$167.11	$167.11	$167.10	$167.10
Purchase #6	$147.77	13.806%	$168.1711	$168.17	$168.15	$168.20
Purchase #7	$209.52	10.155%	$230.7968	$230.80	$230.80	$230.80
7 purchase totals =	$1,154.59		$1,280.4660	$1,280.46	$1,280.40	$1,280.50