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	$234.39	4.849%	$245.7556	$245.76	$245.75	$245.80
Purchase #2	$39.56	5.203%	$41.6183	$41.62	$41.60	$41.60
Purchase #3	$243.98	10.625%	$269.9029	$269.90	$269.90	$269.90
Purchase #4	$135.45	11.288%	$150.7396	$150.74	$150.75	$150.70
Purchase #5	$123.48	3.140%	$127.3573	$127.36	$127.35	$127.40
Purchase #6	$42.47	4.634%	$44.4381	$44.44	$44.45	$44.40
Purchase #7	$39.60	12.790%	$44.6648	$44.66	$44.65	$44.70
7 purchase totals =	$858.93		$924.4766	$924.48	$924.45	$924.50