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	$167.47	13.762%	$190.5172	$190.52	$190.50	$190.50
Purchase #2	$152.42	7.835%	$164.3621	$164.36	$164.35	$164.40
Purchase #3	$244.37	10.173%	$269.2298	$269.23	$269.25	$269.20
Purchase #4	$25.88	11.510%	$28.8588	$28.86	$28.85	$28.90
Purchase #5	$239.45	10.321%	$264.1636	$264.16	$264.15	$264.20
Purchase #6	$52.25	8.645%	$56.767	$56.77	$56.75	$56.80
Purchase #7	$191.71	13.711%	$217.9954	$218.00	$218.00	$218.00
7 purchase totals =	$1,073.55		$1,191.8939	$1,191.90	$1,191.85	$1,192.00