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	$151.78	7.223%	$162.7431	$162.74	$162.75	$162.70
Purchase #2	$65.25	12.790%	$73.5955	$73.60	$73.60	$73.60
Purchase #3	$142.40	9.834%	$156.4036	$156.40	$156.40	$156.40
Purchase #4	$169.45	12.734%	$191.0278	$191.03	$191.05	$191.00
Purchase #5	$231.89	13.779%	$263.8421	$263.84	$263.85	$263.80
Purchase #6	$17.79	11.461%	$19.8289	$19.83	$19.85	$19.80
Purchase #7	$167.40	3.322%	$172.961	$172.96	$172.95	$173.00
7 purchase totals =	$945.96		$1,040.4020	$1,040.40	$1,040.45	$1,040.30