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	$247.49	5.355%	$260.7431	$260.74	$260.75	$260.70
Purchase #2	$228.37	6.104%	$242.3097	$242.31	$242.30	$242.30
Purchase #3	$223.31	5.393%	$235.3531	$235.35	$235.35	$235.40
Purchase #4	$20.86	9.546%	$22.8513	$22.85	$22.85	$22.90
Purchase #5	$208.69	6.168%	$221.562	$221.56	$221.55	$221.60
Purchase #6	$96.86	6.574%	$103.2276	$103.23	$103.25	$103.20
Purchase #7	$39.98	12.857%	$45.1202	$45.12	$45.10	$45.10
7 purchase totals =	$1,065.56		$1,131.1670	$1,131.16	$1,131.15	$1,131.20