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	$106.45	7.499%	$114.4327	$114.43	$114.45	$114.40
Purchase #2	$86.65	5.427%	$91.3525	$91.35	$91.35	$91.40
Purchase #3	$192.55	8.621%	$209.1497	$209.15	$209.15	$209.10
Purchase #4	$76.56	11.474%	$85.3445	$85.34	$85.35	$85.30
Purchase #5	$84.41	7.471%	$90.7163	$90.72	$90.70	$90.70
Purchase #6	$172.74	5.722%	$182.6242	$182.62	$182.60	$182.60
Purchase #7	$245.54	11.549%	$273.8974	$273.90	$273.90	$273.90
7 purchase totals =	$964.90		$1,047.5173	$1,047.51	$1,047.50	$1,047.40