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	$99.39	4.438%	$103.8009	$103.80	$103.80	$103.80
Purchase #2	$103.61	5.244%	$109.0433	$109.04	$109.05	$109.00
Purchase #3	$57.61	8.684%	$62.6129	$62.61	$62.60	$62.60
Purchase #4	$44.86	5.445%	$47.3026	$47.30	$47.30	$47.30
Purchase #5	$147.46	6.417%	$156.9225	$156.92	$156.90	$156.90
Purchase #6	$202.35	10.483%	$223.5624	$223.56	$223.55	$223.60
Purchase #7	$17.35	4.531%	$18.1361	$18.14	$18.15	$18.10
7 purchase totals =	$672.63		$721.3807	$721.37	$721.35	$721.30