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	$149.43	12.614%	$168.2791	$168.28	$168.30	$168.30
Purchase #2	$111.72	10.176%	$123.0886	$123.09	$123.10	$123.10
Purchase #3	$34.61	7.547%	$37.222	$37.22	$37.20	$37.20
Purchase #4	$96.41	5.400%	$101.6161	$101.62	$101.60	$101.60
Purchase #5	$216.46	12.134%	$242.7253	$242.73	$242.75	$242.70
Purchase #6	$69.25	3.325%	$71.5526	$71.55	$71.55	$71.60
Purchase #7	$250.38	12.764%	$282.3385	$282.34	$282.35	$282.30
7 purchase totals =	$928.26		$1,026.8222	$1,026.83	$1,026.85	$1,026.80