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	$179.61	8.283%	$194.4871	$194.49	$194.50	$194.50
Purchase #2	$156.85	7.787%	$169.0639	$169.06	$169.05	$169.10
Purchase #3	$160.53	9.501%	$175.782	$175.78	$175.80	$175.80
Purchase #4	$59.52	9.282%	$65.0446	$65.04	$65.05	$65.00
Purchase #5	$248.35	10.257%	$273.8233	$273.82	$273.80	$273.80
Purchase #6	$82.88	9.726%	$90.9409	$90.94	$90.95	$90.90
Purchase #7	$86.69	5.485%	$91.4449	$91.44	$91.45	$91.40
7 purchase totals =	$974.43		$1,060.5867	$1,060.57	$1,060.60	$1,060.50