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	$149.50	9.795%	$164.1435	$164.14	$164.15	$164.10
Purchase #2	$187.68	13.734%	$213.456	$213.46	$213.45	$213.50
Purchase #3	$38.88	9.616%	$42.6187	$42.62	$42.60	$42.60
Purchase #4	$26.92	6.432%	$28.6515	$28.65	$28.65	$28.70
Purchase #5	$144.36	11.394%	$160.8084	$160.81	$160.80	$160.80
Purchase #6	$25.85	11.117%	$28.7237	$28.72	$28.70	$28.70
Purchase #7	$150.83	11.465%	$168.1227	$168.12	$168.10	$168.10
7 purchase totals =	$724.02		$806.5245	$806.52	$806.45	$806.50