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	$168.96	13.406%	$191.6108	$191.61	$191.60	$191.60
Purchase #2	$89.85	9.775%	$98.6328	$98.63	$98.65	$98.60
Purchase #3	$152.78	3.393%	$157.9638	$157.96	$157.95	$158.00
Purchase #4	$136.91	11.140%	$152.1618	$152.16	$152.15	$152.20
Purchase #5	$139.65	4.459%	$145.877	$145.88	$145.90	$145.90
Purchase #6	$154.58	7.414%	$166.0406	$166.04	$166.05	$166.00
Purchase #7	$170.77	13.127%	$193.187	$193.19	$193.20	$193.20
7 purchase totals =	$1,013.50		$1,105.4738	$1,105.47	$1,105.50	$1,105.50