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	$204.93	8.841%	$223.0479	$223.05	$223.05	$223.00
Purchase #2	$89.51	9.507%	$98.0197	$98.02	$98.00	$98.00
Purchase #3	$20.41	10.164%	$22.4845	$22.48	$22.50	$22.50
Purchase #4	$71.47	8.642%	$77.6464	$77.65	$77.65	$77.60
Purchase #5	$90.58	10.856%	$100.4134	$100.41	$100.40	$100.40
Purchase #6	$141.94	7.463%	$152.533	$152.53	$152.55	$152.50
Purchase #7	$234.99	10.116%	$258.7616	$258.76	$258.75	$258.80
7 purchase totals =	$853.83		$932.9065	$932.90	$932.90	$932.80