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	$167.94	10.267%	$185.1824	$185.18	$185.20	$185.20
Purchase #2	$47.97	7.738%	$51.6819	$51.68	$51.70	$51.70
Purchase #3	$178.28	7.309%	$191.3105	$191.31	$191.30	$191.30
Purchase #4	$59.78	4.229%	$62.3081	$62.31	$62.30	$62.30
Purchase #5	$29.94	8.258%	$32.4124	$32.41	$32.40	$32.40
Purchase #6	$96.85	5.160%	$101.8475	$101.85	$101.85	$101.80
Purchase #7	$242.45	10.293%	$267.4054	$267.41	$267.40	$267.40
7 purchase totals =	$823.21		$892.1482	$892.15	$892.15	$892.10