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	$229.35	9.465%	$251.058	$251.06	$251.05	$251.10
Purchase #2	$66.41	12.524%	$74.7272	$74.73	$74.75	$74.70
Purchase #3	$90.53	10.387%	$99.9334	$99.93	$99.95	$99.90
Purchase #4	$46.91	10.345%	$51.7628	$51.76	$51.75	$51.80
Purchase #5	$68.94	13.359%	$78.1497	$78.15	$78.15	$78.10
Purchase #6	$103.37	13.334%	$117.1534	$117.15	$117.15	$117.20
Purchase #7	$77.57	10.196%	$85.479	$85.48	$85.50	$85.50
7 purchase totals =	$683.08		$758.2635	$758.26	$758.30	$758.30