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	$71.61	11.407%	$79.7786	$79.78	$79.80	$79.80
Purchase #2	$90.66	9.304%	$99.095	$99.10	$99.10	$99.10
Purchase #3	$108.30	5.108%	$113.832	$113.83	$113.85	$113.80
Purchase #4	$69.91	11.439%	$77.907	$77.91	$77.90	$77.90
Purchase #5	$154.51	7.423%	$165.9793	$165.98	$166.00	$166.00
Purchase #6	$122.55	4.390%	$127.9299	$127.93	$127.95	$127.90
Purchase #7	$37.69	8.753%	$40.989	$40.99	$41.00	$41.00
7 purchase totals =	$655.23		$705.5108	$705.52	$705.60	$705.50