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	$128.49	12.791%	$144.9252	$144.93	$144.95	$144.90
Purchase #2	$133.56	10.598%	$147.7147	$147.71	$147.70	$147.70
Purchase #3	$180.55	12.830%	$203.7146	$203.71	$203.70	$203.70
Purchase #4	$154.72	13.443%	$175.519	$175.52	$175.50	$175.50
Purchase #5	$180.84	3.114%	$186.4714	$186.47	$186.45	$186.50
Purchase #6	$95.78	6.423%	$101.9319	$101.93	$101.95	$101.90
Purchase #7	$125.82	11.202%	$139.9144	$139.91	$139.90	$139.90
7 purchase totals =	$999.76		$1,100.1912	$1,100.18	$1,100.15	$1,100.10