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	$119.99	6.636%	$127.9525	$127.95	$127.95	$128.00
Purchase #2	$120.70	10.736%	$133.6584	$133.66	$133.65	$133.70
Purchase #3	$57.83	11.801%	$64.6545	$64.65	$64.65	$64.70
Purchase #4	$162.46	11.320%	$180.8505	$180.85	$180.85	$180.90
Purchase #5	$231.48	10.797%	$256.4729	$256.47	$256.45	$256.50
Purchase #6	$239.59	13.486%	$271.9011	$271.90	$271.90	$271.90
Purchase #7	$54.52	3.634%	$56.5013	$56.50	$56.50	$56.50
7 purchase totals =	$986.57		$1,091.9912	$1,091.98	$1,091.95	$1,092.20