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	$81.38	13.382%	$92.2703	$92.27	$92.25	$92.30
Purchase #2	$59.42	6.462%	$63.2597	$63.26	$63.25	$63.30
Purchase #3	$158.41	10.267%	$174.674	$174.67	$174.65	$174.70
Purchase #4	$193.30	12.457%	$217.3794	$217.38	$217.40	$217.40
Purchase #5	$90.84	11.806%	$101.5646	$101.56	$101.55	$101.60
Purchase #6	$134.62	13.738%	$153.1141	$153.11	$153.10	$153.10
Purchase #7	$245.56	7.704%	$264.4779	$264.48	$264.50	$264.50
7 purchase totals =	$963.53		$1,066.7400	$1,066.73	$1,066.70	$1,066.90