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	$141.82	7.605%	$152.6054	$152.61	$152.60	$152.60
Purchase #2	$200.57	9.407%	$219.4376	$219.44	$219.45	$219.40
Purchase #3	$46.70	8.171%	$50.5159	$50.52	$50.50	$50.50
Purchase #4	$26.71	4.463%	$27.9021	$27.90	$27.90	$27.90
Purchase #5	$128.93	9.606%	$141.315	$141.32	$141.30	$141.30
Purchase #6	$42.74	5.450%	$45.0693	$45.07	$45.05	$45.10
Purchase #7	$6.44	5.856%	$6.8171	$6.82	$6.80	$6.80
7 purchase totals =	$593.91		$643.6624	$643.68	$643.60	$643.60