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	$71.48	8.391%	$77.4779	$77.48	$77.50	$77.50
Purchase #2	$76.49	6.595%	$81.5345	$81.53	$81.55	$81.50
Purchase #3	$186.59	5.666%	$197.1622	$197.16	$197.15	$197.20
Purchase #4	$248.38	3.516%	$257.113	$257.11	$257.10	$257.10
Purchase #5	$92.72	7.619%	$99.7843	$99.78	$99.80	$99.80
Purchase #6	$212.90	7.565%	$229.0059	$229.01	$229.00	$229.00
Purchase #7	$176.89	13.253%	$200.3332	$200.33	$200.35	$200.30
7 purchase totals =	$1,065.45		$1,142.4110	$1,142.40	$1,142.45	$1,142.40