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	$139.35	8.541%	$151.2519	$151.25	$151.25	$151.30
Purchase #2	$209.28	3.630%	$216.8769	$216.88	$216.90	$216.90
Purchase #3	$165.96	11.231%	$184.599	$184.60	$184.60	$184.60
Purchase #4	$126.92	9.689%	$139.2173	$139.22	$139.20	$139.20
Purchase #5	$37.26	13.765%	$42.3888	$42.39	$42.40	$42.40
Purchase #6	$47.25	11.115%	$52.5018	$52.50	$52.50	$52.50
Purchase #7	$171.30	6.232%	$181.9754	$181.98	$182.00	$182.00
7 purchase totals =	$897.32		$968.8111	$968.82	$968.85	$968.90