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	$112.29	13.745%	$127.7243	$127.72	$127.70	$127.70
Purchase #2	$42.71	7.600%	$45.956	$45.96	$45.95	$46.00
Purchase #3	$144.41	6.739%	$154.1418	$154.14	$154.15	$154.10
Purchase #4	$206.57	8.134%	$223.3724	$223.37	$223.35	$223.40
Purchase #5	$137.88	3.287%	$142.4121	$142.41	$142.40	$142.40
Purchase #6	$214.71	5.797%	$227.1567	$227.16	$227.15	$227.20
Purchase #7	$148.98	5.437%	$157.08	$157.08	$157.10	$157.10
7 purchase totals =	$1,007.55		$1,077.8433	$1,077.84	$1,077.80	$1,077.90