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	$80.52	6.605%	$85.8383	$85.84	$85.85	$85.80
Purchase #2	$144.72	4.433%	$151.1354	$151.14	$151.15	$151.10
Purchase #3	$37.41	11.472%	$41.7017	$41.70	$41.70	$41.70
Purchase #4	$188.31	11.106%	$209.2237	$209.22	$209.20	$209.20
Purchase #5	$170.58	7.717%	$183.7437	$183.74	$183.75	$183.70
Purchase #6	$146.64	6.617%	$156.3432	$156.34	$156.35	$156.30
Purchase #7	$154.72	13.744%	$175.9847	$175.98	$176.00	$176.00
7 purchase totals =	$922.90		$1,003.9707	$1,003.96	$1,004.00	$1,003.80