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	$26.59	8.523%	$28.8563	$28.86	$28.85	$28.90
Purchase #2	$29.71	4.711%	$31.1096	$31.11	$31.10	$31.10
Purchase #3	$125.52	4.253%	$130.8584	$130.86	$130.85	$130.90
Purchase #4	$137.42	7.377%	$147.5575	$147.56	$147.55	$147.60
Purchase #5	$44.44	13.685%	$50.5216	$50.52	$50.50	$50.50
Purchase #6	$182.34	11.431%	$203.1833	$203.18	$203.20	$203.20
Purchase #7	$152.54	5.474%	$160.89	$160.89	$160.90	$160.90
7 purchase totals =	$698.56		$752.9767	$752.98	$752.95	$753.10