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	$43.96	6.107%	$46.6446	$46.64	$46.65	$46.60
Purchase #2	$85.92	8.792%	$93.4741	$93.47	$93.45	$93.50
Purchase #3	$72.90	13.596%	$82.8115	$82.81	$82.80	$82.80
Purchase #4	$186.59	9.581%	$204.4672	$204.47	$204.45	$204.50
Purchase #5	$196.43	6.429%	$209.0585	$209.06	$209.05	$209.10
Purchase #6	$131.48	4.834%	$137.8357	$137.84	$137.85	$137.80
Purchase #7	$99.29	3.642%	$102.9061	$102.91	$102.90	$102.90
7 purchase totals =	$816.57		$877.1977	$877.20	$877.15	$877.20