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	$132.33	11.481%	$147.5228	$147.52	$147.50	$147.50
Purchase #2	$111.39	12.862%	$125.717	$125.72	$125.70	$125.70
Purchase #3	$24.87	13.310%	$28.1802	$28.18	$28.20	$28.20
Purchase #4	$216.41	3.241%	$223.4238	$223.42	$223.40	$223.40
Purchase #5	$246.89	7.361%	$265.0636	$265.06	$265.05	$265.10
Purchase #6	$188.31	4.478%	$196.7425	$196.74	$196.75	$196.70
Purchase #7	$117.78	4.442%	$123.0118	$123.01	$123.00	$123.00
7 purchase totals =	$1,037.98		$1,109.6617	$1,109.65	$1,109.60	$1,109.60