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	$124.33	7.181%	$133.2581	$133.26	$133.25	$133.30
Purchase #2	$90.52	3.399%	$93.5968	$93.60	$93.60	$93.60
Purchase #3	$116.82	5.323%	$123.0383	$123.04	$123.05	$123.00
Purchase #4	$123.75	12.568%	$139.3029	$139.30	$139.30	$139.30
Purchase #5	$192.56	6.620%	$205.3075	$205.31	$205.30	$205.30
Purchase #6	$61.65	10.566%	$68.1639	$68.16	$68.15	$68.20
Purchase #7	$10.50	3.121%	$10.8277	$10.83	$10.85	$10.80
7 purchase totals =	$720.13		$773.4952	$773.50	$773.50	$773.50