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	$58.43	4.598%	$61.1166	$61.12	$61.10	$61.10
Purchase #2	$90.42	3.224%	$93.3351	$93.34	$93.35	$93.30
Purchase #3	$59.77	3.789%	$62.0347	$62.03	$62.05	$62.00
Purchase #4	$139.62	6.278%	$148.3853	$148.39	$148.40	$148.40
Purchase #5	$50.90	8.597%	$55.2759	$55.28	$55.30	$55.30
Purchase #6	$116.38	10.356%	$128.4323	$128.43	$128.45	$128.40
Purchase #7	$183.41	6.852%	$195.9773	$195.98	$196.00	$196.00
7 purchase totals =	$698.93		$744.5572	$744.57	$744.65	$744.50