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	$85.59	12.244%	$96.0696	$96.07	$96.05	$96.10
Purchase #2	$131.36	8.432%	$142.4363	$142.44	$142.45	$142.40
Purchase #3	$47.70	7.695%	$51.3705	$51.37	$51.35	$51.40
Purchase #4	$48.81	13.741%	$55.517	$55.52	$55.50	$55.50
Purchase #5	$91.78	8.319%	$99.4152	$99.42	$99.40	$99.40
Purchase #6	$5.46	10.611%	$6.0394	$6.04	$6.05	$6.00
Purchase #7	$145.64	10.262%	$160.5856	$160.59	$160.60	$160.60
7 purchase totals =	$556.34		$611.4336	$611.45	$611.40	$611.40