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	$78.49	9.233%	$85.737	$85.74	$85.75	$85.70
Purchase #2	$66.45	8.490%	$72.0916	$72.09	$72.10	$72.10
Purchase #3	$170.67	8.653%	$185.4381	$185.44	$185.45	$185.40
Purchase #4	$142.93	5.586%	$150.9141	$150.91	$150.90	$150.90
Purchase #5	$115.42	10.365%	$127.3833	$127.38	$127.40	$127.40
Purchase #6	$71.64	11.588%	$79.9416	$79.94	$79.95	$79.90
Purchase #7	$62.74	12.200%	$70.3943	$70.39	$70.40	$70.40
7 purchase totals =	$708.34		$771.9000	$771.89	$771.95	$771.80