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	$56.55	7.196%	$60.6193	$60.62	$60.60	$60.60
Purchase #2	$119.27	6.681%	$127.2384	$127.24	$127.25	$127.20
Purchase #3	$121.41	7.310%	$130.2851	$130.29	$130.30	$130.30
Purchase #4	$189.34	13.739%	$215.3534	$215.35	$215.35	$215.40
Purchase #5	$18.79	7.266%	$20.1553	$20.16	$20.15	$20.20
Purchase #6	$82.83	8.831%	$90.1447	$90.14	$90.15	$90.10
Purchase #7	$176.71	3.326%	$182.5874	$182.59	$182.60	$182.60
7 purchase totals =	$764.90		$826.3836	$826.39	$826.40	$826.40