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	$92.83	9.318%	$101.4799	$101.48	$101.50	$101.50
Purchase #2	$43.82	13.657%	$49.8045	$49.80	$49.80	$49.80
Purchase #3	$73.77	12.156%	$82.7375	$82.74	$82.75	$82.70
Purchase #4	$190.62	10.113%	$209.8974	$209.90	$209.90	$209.90
Purchase #5	$145.89	13.839%	$166.0797	$166.08	$166.10	$166.10
Purchase #6	$9.68	7.207%	$10.3776	$10.38	$10.40	$10.40
Purchase #7	$146.85	10.368%	$162.0754	$162.08	$162.10	$162.10
7 purchase totals =	$703.46		$782.4520	$782.46	$782.55	$782.50