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	$178.71	9.821%	$196.2611	$196.26	$196.25	$196.30
Purchase #2	$36.71	9.192%	$40.0844	$40.08	$40.10	$40.10
Purchase #3	$48.55	4.780%	$50.8707	$50.87	$50.85	$50.90
Purchase #4	$216.90	9.618%	$237.7614	$237.76	$237.75	$237.80
Purchase #5	$174.90	7.748%	$188.4513	$188.45	$188.45	$188.50
Purchase #6	$18.87	11.632%	$21.065	$21.07	$21.05	$21.10
Purchase #7	$239.95	12.278%	$269.4111	$269.41	$269.40	$269.40
7 purchase totals =	$914.59		$1,003.9050	$1,003.90	$1,003.85	$1,004.10