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	$41.76	11.455%	$46.5436	$46.54	$46.55	$46.50
Purchase #2	$221.72	10.674%	$245.3864	$245.39	$245.40	$245.40
Purchase #3	$233.48	7.502%	$250.9957	$251.00	$251.00	$251.00
Purchase #4	$55.97	6.107%	$59.3881	$59.39	$59.40	$59.40
Purchase #5	$238.91	11.142%	$265.5294	$265.53	$265.55	$265.50
Purchase #6	$210.75	4.847%	$220.9651	$220.97	$220.95	$221.00
Purchase #7	$140.86	10.820%	$156.1011	$156.10	$156.10	$156.10
7 purchase totals =	$1,143.45		$1,244.9094	$1,244.92	$1,244.95	$1,244.90