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	$99.59	7.553%	$107.112	$107.11	$107.10	$107.10
Purchase #2	$47.40	6.702%	$50.5767	$50.58	$50.60	$50.60
Purchase #3	$48.76	10.793%	$54.0227	$54.02	$54.00	$54.00
Purchase #4	$96.77	9.283%	$105.7532	$105.75	$105.75	$105.80
Purchase #5	$20.32	7.521%	$21.8483	$21.85	$21.85	$21.80
Purchase #6	$65.63	9.703%	$71.9981	$72.00	$72.00	$72.00
Purchase #7	$137.42	5.685%	$145.2323	$145.23	$145.25	$145.20
7 purchase totals =	$515.89		$556.5433	$556.54	$556.55	$556.50