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	$219.80	4.740%	$230.2185	$230.22	$230.20	$230.20
Purchase #2	$94.75	6.428%	$100.8405	$100.84	$100.85	$100.80
Purchase #3	$209.52	11.673%	$233.9773	$233.98	$234.00	$234.00
Purchase #4	$30.64	7.152%	$32.8314	$32.83	$32.85	$32.80
Purchase #5	$173.41	3.549%	$179.5643	$179.56	$179.55	$179.60
Purchase #6	$221.97	12.582%	$249.8983	$249.90	$249.90	$249.90
Purchase #7	$35.54	4.455%	$37.1233	$37.12	$37.10	$37.10
7 purchase totals =	$985.63		$1,064.4536	$1,064.45	$1,064.45	$1,064.40