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	$109.83	3.707%	$113.9014	$113.90	$113.90	$113.90
Purchase #2	$115.44	13.217%	$130.6977	$130.70	$130.70	$130.70
Purchase #3	$96.44	4.261%	$100.5493	$100.55	$100.55	$100.50
Purchase #4	$43.89	9.232%	$47.9419	$47.94	$47.95	$47.90
Purchase #5	$165.56	3.595%	$171.5119	$171.51	$171.50	$171.50
Purchase #6	$69.83	10.818%	$77.3842	$77.38	$77.40	$77.40
Purchase #7	$211.67	10.244%	$233.3535	$233.35	$233.35	$233.40
7 purchase totals =	$812.66		$875.3399	$875.33	$875.35	$875.30