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	$142.63	6.254%	$151.5501	$151.55	$151.55	$151.60
Purchase #2	$6.83	6.476%	$7.2723	$7.27	$7.25	$7.30
Purchase #3	$74.60	10.591%	$82.5009	$82.50	$82.50	$82.50
Purchase #4	$161.91	4.719%	$169.5505	$169.55	$169.55	$169.60
Purchase #5	$52.33	7.716%	$56.3678	$56.37	$56.35	$56.40
Purchase #6	$213.71	4.537%	$223.406	$223.41	$223.40	$223.40
Purchase #7	$30.71	10.201%	$33.8427	$33.84	$33.85	$33.80
7 purchase totals =	$682.72		$724.4903	$724.49	$724.45	$724.60