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	$206.54	4.125%	$215.0598	$215.06	$215.05	$215.10
Purchase #2	$212.65	11.277%	$236.6305	$236.63	$236.65	$236.60
Purchase #3	$96.56	5.792%	$102.1528	$102.15	$102.15	$102.20
Purchase #4	$100.78	7.542%	$108.3808	$108.38	$108.40	$108.40
Purchase #5	$61.40	10.564%	$67.8863	$67.89	$67.90	$67.90
Purchase #6	$188.57	6.348%	$200.5404	$200.54	$200.55	$200.50
Purchase #7	$99.29	11.519%	$110.7272	$110.73	$110.75	$110.70
7 purchase totals =	$965.79		$1,041.3778	$1,041.38	$1,041.45	$1,041.40