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	$108.62	6.539%	$115.7227	$115.72	$115.70	$115.70
Purchase #2	$140.72	9.534%	$154.1362	$154.14	$154.15	$154.10
Purchase #3	$123.50	3.408%	$127.7089	$127.71	$127.70	$127.70
Purchase #4	$224.67	8.369%	$243.4726	$243.47	$243.45	$243.50
Purchase #5	$127.80	13.772%	$145.4006	$145.40	$145.40	$145.40
Purchase #6	$174.77	13.588%	$198.5177	$198.52	$198.50	$198.50
Purchase #7	$73.54	12.567%	$82.7818	$82.78	$82.80	$82.80
7 purchase totals =	$973.62		$1,067.7405	$1,067.74	$1,067.70	$1,067.70