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	$54.72	8.757%	$59.5118	$59.51	$59.50	$59.50
Purchase #2	$182.69	5.465%	$192.674	$192.67	$192.65	$192.70
Purchase #3	$212.38	13.848%	$241.7904	$241.79	$241.80	$241.80
Purchase #4	$232.70	8.254%	$251.9071	$251.91	$251.90	$251.90
Purchase #5	$40.90	12.841%	$46.152	$46.15	$46.15	$46.20
Purchase #6	$63.80	6.294%	$67.8156	$67.82	$67.80	$67.80
Purchase #7	$232.57	7.630%	$250.3151	$250.32	$250.30	$250.30
7 purchase totals =	$1,019.76		$1,110.1660	$1,110.17	$1,110.10	$1,110.20