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	$134.92	13.540%	$153.1882	$153.19	$153.20	$153.20
Purchase #2	$62.29	8.470%	$67.566	$67.57	$67.55	$67.60
Purchase #3	$192.73	4.237%	$200.896	$200.90	$200.90	$200.90
Purchase #4	$237.59	9.658%	$260.5364	$260.54	$260.55	$260.50
Purchase #5	$35.77	9.263%	$39.0834	$39.08	$39.10	$39.10
Purchase #6	$232.66	13.821%	$264.8159	$264.82	$264.80	$264.80
Purchase #7	$98.34	11.463%	$109.6127	$109.61	$109.60	$109.60
7 purchase totals =	$994.30		$1,095.6986	$1,095.71	$1,095.70	$1,095.70