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	$139.29	13.451%	$158.0259	$158.03	$158.05	$158.00
Purchase #2	$240.95	13.353%	$273.1241	$273.12	$273.10	$273.10
Purchase #3	$65.32	3.504%	$67.6088	$67.61	$67.60	$67.60
Purchase #4	$89.61	6.371%	$95.3191	$95.32	$95.30	$95.30
Purchase #5	$27.56	5.732%	$29.1397	$29.14	$29.15	$29.10
Purchase #6	$223.46	12.586%	$251.5847	$251.58	$251.60	$251.60
Purchase #7	$189.91	4.467%	$198.3933	$198.39	$198.40	$198.40
7 purchase totals =	$976.10		$1,073.1956	$1,073.19	$1,073.20	$1,073.10