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	$222.77	8.377%	$241.4314	$241.43	$241.45	$241.40
Purchase #2	$249.76	6.872%	$266.9235	$266.92	$266.90	$266.90
Purchase #3	$250.86	7.829%	$270.4998	$270.50	$270.50	$270.50
Purchase #4	$141.63	6.621%	$151.0073	$151.01	$151.00	$151.00
Purchase #5	$145.40	11.629%	$162.3086	$162.31	$162.30	$162.30
Purchase #6	$88.50	12.810%	$99.8369	$99.84	$99.85	$99.80
Purchase #7	$243.39	7.572%	$261.8195	$261.82	$261.80	$261.80
7 purchase totals =	$1,342.31		$1,453.8270	$1,453.83	$1,453.80	$1,453.70