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	$69.33	12.591%	$78.0593	$78.06	$78.05	$78.10
Purchase #2	$203.56	7.858%	$219.5557	$219.56	$219.55	$219.60
Purchase #3	$184.92	5.658%	$195.3828	$195.38	$195.40	$195.40
Purchase #4	$242.94	8.491%	$263.568	$263.57	$263.55	$263.60
Purchase #5	$127.44	11.111%	$141.5999	$141.60	$141.60	$141.60
Purchase #6	$168.58	13.666%	$191.6181	$191.62	$191.60	$191.60
Purchase #7	$55.95	9.527%	$61.2804	$61.28	$61.30	$61.30
7 purchase totals =	$1,052.72		$1,151.0642	$1,151.07	$1,151.05	$1,151.20