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	$18.66	5.778%	$19.7382	$19.74	$19.75	$19.70
Purchase #2	$196.33	13.213%	$222.2711	$222.27	$222.25	$222.30
Purchase #3	$206.50	4.250%	$215.2763	$215.28	$215.30	$215.30
Purchase #4	$77.89	7.110%	$83.428	$83.43	$83.45	$83.40
Purchase #5	$96.51	10.710%	$106.8462	$106.85	$106.85	$106.80
Purchase #6	$23.98	13.814%	$27.2926	$27.29	$27.30	$27.30
Purchase #7	$83.35	11.451%	$92.8944	$92.89	$92.90	$92.90
7 purchase totals =	$703.22		$767.7468	$767.75	$767.80	$767.70