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	$116.75	3.154%	$120.4323	$120.43	$120.45	$120.40
Purchase #2	$203.93	9.459%	$223.2197	$223.22	$223.20	$223.20
Purchase #3	$168.52	13.374%	$191.0579	$191.06	$191.05	$191.10
Purchase #4	$242.77	9.696%	$266.309	$266.31	$266.30	$266.30
Purchase #5	$50.29	10.190%	$55.4146	$55.41	$55.40	$55.40
Purchase #6	$62.71	4.380%	$65.4567	$65.46	$65.45	$65.50
Purchase #7	$49.48	10.479%	$54.665	$54.67	$54.65	$54.70
7 purchase totals =	$894.45		$976.5552	$976.56	$976.50	$976.60