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	$40.91	12.283%	$45.935	$45.94	$45.95	$45.90
Purchase #2	$18.96	11.113%	$21.067	$21.07	$21.05	$21.10
Purchase #3	$188.30	11.308%	$209.593	$209.59	$209.60	$209.60
Purchase #4	$134.73	13.842%	$153.3793	$153.38	$153.40	$153.40
Purchase #5	$113.36	8.552%	$123.0545	$123.05	$123.05	$123.10
Purchase #6	$104.92	10.181%	$115.6019	$115.60	$115.60	$115.60
Purchase #7	$33.77	12.872%	$38.1169	$38.12	$38.10	$38.10
7 purchase totals =	$634.95		$706.7476	$706.75	$706.75	$706.80