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	$97.82	7.400%	$105.0587	$105.06	$105.05	$105.10
Purchase #2	$152.52	8.537%	$165.5406	$165.54	$165.55	$165.50
Purchase #3	$28.34	8.745%	$30.8183	$30.82	$30.80	$30.80
Purchase #4	$49.75	10.214%	$54.8315	$54.83	$54.85	$54.80
Purchase #5	$104.54	4.564%	$109.3112	$109.31	$109.30	$109.30
Purchase #6	$105.73	4.563%	$110.5545	$110.55	$110.55	$110.60
Purchase #7	$50.42	9.156%	$55.0365	$55.04	$55.05	$55.00
7 purchase totals =	$589.12		$631.1513	$631.15	$631.15	$631.10