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	$145.52	8.529%	$157.9314	$157.93	$157.95	$157.90
Purchase #2	$58.38	6.399%	$62.1157	$62.12	$62.10	$62.10
Purchase #3	$245.57	8.568%	$266.6104	$266.61	$266.60	$266.60
Purchase #4	$171.71	5.117%	$180.4964	$180.50	$180.50	$180.50
Purchase #5	$185.34	12.693%	$208.8652	$208.87	$208.85	$208.90
Purchase #6	$171.34	7.123%	$183.5445	$183.54	$183.55	$183.50
Purchase #7	$25.60	7.784%	$27.5927	$27.59	$27.60	$27.60
7 purchase totals =	$1,003.46		$1,087.1563	$1,087.16	$1,087.15	$1,087.10