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	$26.63	10.232%	$29.3548	$29.35	$29.35	$29.40
Purchase #2	$42.74	7.459%	$45.928	$45.93	$45.95	$45.90
Purchase #3	$11.41	11.564%	$12.7295	$12.73	$12.75	$12.70
Purchase #4	$94.95	9.690%	$104.1507	$104.15	$104.15	$104.20
Purchase #5	$64.83	9.518%	$71.0005	$71.00	$71.00	$71.00
Purchase #6	$98.30	6.649%	$104.836	$104.84	$104.85	$104.80
Purchase #7	$42.86	13.855%	$48.7983	$48.80	$48.80	$48.80
7 purchase totals =	$381.72		$416.7978	$416.80	$416.85	$416.80