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	$32.67	13.361%	$37.035	$37.04	$37.05	$37.00
Purchase #2	$144.40	11.117%	$160.4529	$160.45	$160.45	$160.50
Purchase #3	$242.64	7.850%	$261.6872	$261.69	$261.70	$261.70
Purchase #4	$37.61	7.391%	$40.3898	$40.39	$40.40	$40.40
Purchase #5	$73.98	8.465%	$80.2424	$80.24	$80.25	$80.20
Purchase #6	$210.69	10.579%	$232.9789	$232.98	$233.00	$233.00
Purchase #7	$202.31	7.806%	$218.1023	$218.10	$218.10	$218.10
7 purchase totals =	$944.30		$1,030.8885	$1,030.89	$1,030.95	$1,030.90