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	$166.67	3.198%	$172.0001	$172.00	$172.00	$172.00
Purchase #2	$40.78	4.495%	$42.6131	$42.61	$42.60	$42.60
Purchase #3	$43.76	5.555%	$46.1909	$46.19	$46.20	$46.20
Purchase #4	$163.27	11.459%	$181.9791	$181.98	$182.00	$182.00
Purchase #5	$124.77	9.244%	$136.3037	$136.30	$136.30	$136.30
Purchase #6	$21.72	13.338%	$24.617	$24.62	$24.60	$24.60
Purchase #7	$132.52	11.228%	$147.3993	$147.40	$147.40	$147.40
7 purchase totals =	$693.49		$751.1032	$751.10	$751.10	$751.10