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	$39.75	6.150%	$42.1946	$42.19	$42.20	$42.20
Purchase #2	$84.64	11.704%	$94.5463	$94.55	$94.55	$94.50
Purchase #3	$65.56	11.374%	$73.0168	$73.02	$73.00	$73.00
Purchase #4	$191.34	9.648%	$209.8005	$209.80	$209.80	$209.80
Purchase #5	$124.55	4.701%	$130.4051	$130.41	$130.40	$130.40
Purchase #6	$172.42	7.377%	$185.1394	$185.14	$185.15	$185.10
Purchase #7	$250.40	12.226%	$281.0139	$281.01	$281.00	$281.00
7 purchase totals =	$928.66		$1,016.1166	$1,016.12	$1,016.10	$1,016.00