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	$55.66	3.128%	$57.401	$57.40	$57.40	$57.40
Purchase #2	$152.65	4.832%	$160.026	$160.03	$160.05	$160.00
Purchase #3	$165.86	4.393%	$173.1462	$173.15	$173.15	$173.10
Purchase #4	$246.41	4.864%	$258.3954	$258.40	$258.40	$258.40
Purchase #5	$185.92	12.645%	$209.4296	$209.43	$209.45	$209.40
Purchase #6	$184.46	3.695%	$191.2758	$191.28	$191.30	$191.30
Purchase #7	$185.58	12.385%	$208.5641	$208.56	$208.55	$208.60
7 purchase totals =	$1,176.54		$1,258.2381	$1,258.25	$1,258.30	$1,258.20