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	$228.74	9.297%	$250.006	$250.01	$250.00	$250.00
Purchase #2	$63.46	11.517%	$70.7687	$70.77	$70.75	$70.80
Purchase #3	$192.49	9.268%	$210.33	$210.33	$210.35	$210.30
Purchase #4	$242.94	6.562%	$258.8817	$258.88	$258.90	$258.90
Purchase #5	$18.52	12.689%	$20.87	$20.87	$20.85	$20.90
Purchase #6	$200.28	10.669%	$221.6479	$221.65	$221.65	$221.60
Purchase #7	$18.84	9.443%	$20.6191	$20.62	$20.60	$20.60
7 purchase totals =	$965.27		$1,053.1234	$1,053.13	$1,053.10	$1,053.10