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	$164.98	5.480%	$174.0209	$174.02	$174.00	$174.00
Purchase #2	$66.97	8.488%	$72.6544	$72.65	$72.65	$72.70
Purchase #3	$54.76	7.842%	$59.0543	$59.05	$59.05	$59.10
Purchase #4	$38.72	8.512%	$42.0158	$42.02	$42.00	$42.00
Purchase #5	$148.60	10.635%	$164.4036	$164.40	$164.40	$164.40
Purchase #6	$37.71	4.136%	$39.2697	$39.27	$39.25	$39.30
Purchase #7	$29.62	10.680%	$32.7834	$32.78	$32.80	$32.80
7 purchase totals =	$541.36		$584.2021	$584.19	$584.15	$584.30