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	$218.51	12.428%	$245.6664	$245.67	$245.65	$245.70
Purchase #2	$48.57	11.236%	$54.0273	$54.03	$54.05	$54.00
Purchase #3	$97.56	8.326%	$105.6828	$105.68	$105.70	$105.70
Purchase #4	$109.48	6.257%	$116.3302	$116.33	$116.35	$116.30
Purchase #5	$25.85	4.376%	$26.9812	$26.98	$27.00	$27.00
Purchase #6	$88.78	11.316%	$98.8263	$98.83	$98.85	$98.80
Purchase #7	$150.31	11.779%	$168.015	$168.02	$168.00	$168.00
7 purchase totals =	$739.06		$815.5292	$815.54	$815.60	$815.50