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	$117.86	11.508%	$131.4233	$131.42	$131.40	$131.40
Purchase #2	$132.66	3.753%	$137.6387	$137.64	$137.65	$137.60
Purchase #3	$111.66	12.301%	$125.3953	$125.40	$125.40	$125.40
Purchase #4	$165.30	12.219%	$185.498	$185.50	$185.50	$185.50
Purchase #5	$134.73	12.712%	$151.8569	$151.86	$151.85	$151.90
Purchase #6	$156.80	12.823%	$176.9065	$176.91	$176.90	$176.90
Purchase #7	$74.95	4.501%	$78.3235	$78.32	$78.30	$78.30
7 purchase totals =	$893.96		$987.0422	$987.05	$987.00	$987.00