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	$31.65	4.382%	$33.0369	$33.04	$33.05	$33.00
Purchase #2	$171.37	8.600%	$186.1078	$186.11	$186.10	$186.10
Purchase #3	$191.74	4.173%	$199.7413	$199.74	$199.75	$199.70
Purchase #4	$98.59	5.187%	$103.7039	$103.70	$103.70	$103.70
Purchase #5	$150.72	12.697%	$169.8569	$169.86	$169.85	$169.90
Purchase #6	$166.42	11.398%	$185.3886	$185.39	$185.40	$185.40
Purchase #7	$77.67	6.364%	$82.6129	$82.61	$82.60	$82.60
7 purchase totals =	$888.16		$960.4483	$960.45	$960.45	$960.40