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	$234.91	6.612%	$250.4422	$250.44	$250.45	$250.40
Purchase #2	$105.56	7.856%	$113.8528	$113.85	$113.85	$113.90
Purchase #3	$183.69	6.818%	$196.214	$196.21	$196.20	$196.20
Purchase #4	$94.32	5.640%	$99.6396	$99.64	$99.65	$99.60
Purchase #5	$150.99	4.183%	$157.3059	$157.31	$157.30	$157.30
Purchase #6	$57.66	3.780%	$59.8395	$59.84	$59.85	$59.80
Purchase #7	$150.52	6.672%	$160.5627	$160.56	$160.55	$160.60
7 purchase totals =	$977.65		$1,037.8567	$1,037.85	$1,037.85	$1,037.80