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	$83.28	5.594%	$87.9387	$87.94	$87.95	$87.90
Purchase #2	$244.94	6.539%	$260.9566	$260.96	$260.95	$261.00
Purchase #3	$224.58	10.250%	$247.5995	$247.60	$247.60	$247.60
Purchase #4	$90.42	9.870%	$99.3445	$99.34	$99.35	$99.30
Purchase #5	$62.91	7.168%	$67.4194	$67.42	$67.40	$67.40
Purchase #6	$240.71	9.497%	$263.5702	$263.57	$263.55	$263.60
Purchase #7	$37.36	7.317%	$40.0936	$40.09	$40.10	$40.10
7 purchase totals =	$984.20		$1,066.9225	$1,066.92	$1,066.90	$1,066.90