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	$226.41	10.173%	$249.4427	$249.44	$249.45	$249.40
Purchase #2	$89.42	12.362%	$100.4741	$100.47	$100.45	$100.50
Purchase #3	$88.30	4.618%	$92.3777	$92.38	$92.40	$92.40
Purchase #4	$228.49	4.358%	$238.4476	$238.45	$238.45	$238.40
Purchase #5	$62.55	13.399%	$70.9311	$70.93	$70.95	$70.90
Purchase #6	$8.42	11.521%	$9.3901	$9.39	$9.40	$9.40
Purchase #7	$48.80	11.393%	$54.3598	$54.36	$54.35	$54.40
7 purchase totals =	$752.39		$815.4231	$815.42	$815.45	$815.40