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	$53.92	11.768%	$60.2653	$60.27	$60.25	$60.30
Purchase #2	$166.30	11.412%	$185.2782	$185.28	$185.30	$185.30
Purchase #3	$63.87	3.138%	$65.8742	$65.87	$65.85	$65.90
Purchase #4	$65.45	9.279%	$71.5231	$71.52	$71.50	$71.50
Purchase #5	$44.99	13.470%	$51.0502	$51.05	$51.05	$51.10
Purchase #6	$152.91	6.374%	$162.6565	$162.66	$162.65	$162.70
Purchase #7	$25.60	12.655%	$28.8397	$28.84	$28.85	$28.80
7 purchase totals =	$573.04		$625.4872	$625.49	$625.45	$625.60