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	$171.57	9.721%	$188.2483	$188.25	$188.25	$188.20
Purchase #2	$174.34	9.723%	$191.2911	$191.29	$191.30	$191.30
Purchase #3	$212.54	12.188%	$238.4444	$238.44	$238.45	$238.40
Purchase #4	$143.97	8.858%	$156.7229	$156.72	$156.70	$156.70
Purchase #5	$121.92	7.151%	$130.6385	$130.64	$130.65	$130.60
Purchase #6	$93.84	6.164%	$99.6243	$99.62	$99.60	$99.60
Purchase #7	$19.61	4.353%	$20.4636	$20.46	$20.45	$20.50
7 purchase totals =	$937.79		$1,025.4331	$1,025.42	$1,025.40	$1,025.30