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	$101.92	6.115%	$108.1524	$108.15	$108.15	$108.20
Purchase #2	$197.70	6.109%	$209.7775	$209.78	$209.80	$209.80
Purchase #3	$91.37	11.643%	$102.0082	$102.01	$102.00	$102.00
Purchase #4	$217.78	12.539%	$245.0874	$245.09	$245.10	$245.10
Purchase #5	$61.69	5.456%	$65.0558	$65.06	$65.05	$65.10
Purchase #6	$125.52	10.235%	$138.367	$138.37	$138.35	$138.40
Purchase #7	$130.41	13.791%	$148.3948	$148.39	$148.40	$148.40
7 purchase totals =	$926.39		$1,016.8431	$1,016.85	$1,016.85	$1,017.00