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	$229.48	7.257%	$246.1334	$246.13	$246.15	$246.10
Purchase #2	$51.63	6.533%	$55.003	$55.00	$55.00	$55.00
Purchase #3	$81.77	9.837%	$89.8137	$89.81	$89.80	$89.80
Purchase #4	$152.83	6.202%	$162.3085	$162.31	$162.30	$162.30
Purchase #5	$231.63	8.160%	$250.531	$250.53	$250.55	$250.50
Purchase #6	$229.26	5.216%	$241.2182	$241.22	$241.20	$241.20
Purchase #7	$17.86	12.227%	$20.0437	$20.04	$20.05	$20.00
7 purchase totals =	$994.46		$1,065.0515	$1,065.04	$1,065.05	$1,064.90