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	$211.94	3.857%	$220.1145	$220.11	$220.10	$220.10
Purchase #2	$63.72	5.498%	$67.2233	$67.22	$67.20	$67.20
Purchase #3	$89.36	5.342%	$94.1336	$94.13	$94.15	$94.10
Purchase #4	$222.51	12.691%	$250.7487	$250.75	$250.75	$250.70
Purchase #5	$73.33	13.202%	$83.011	$83.01	$83.00	$83.00
Purchase #6	$184.92	6.250%	$196.4775	$196.48	$196.50	$196.50
Purchase #7	$38.77	3.562%	$40.151	$40.15	$40.15	$40.20
7 purchase totals =	$884.55		$951.8596	$951.85	$951.85	$951.80