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	$66.27	4.302%	$69.1209	$69.12	$69.10	$69.10
Purchase #2	$175.66	7.269%	$188.4287	$188.43	$188.45	$188.40
Purchase #3	$230.61	8.187%	$249.49	$249.49	$249.50	$249.50
Purchase #4	$89.33	12.524%	$100.5177	$100.52	$100.50	$100.50
Purchase #5	$29.79	12.641%	$33.5558	$33.56	$33.55	$33.60
Purchase #6	$56.51	4.852%	$59.2519	$59.25	$59.25	$59.30
Purchase #7	$31.35	8.501%	$34.0151	$34.02	$34.00	$34.00
7 purchase totals =	$679.52		$734.3801	$734.39	$734.35	$734.40