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	$208.97	13.399%	$236.9699	$236.97	$236.95	$237.00
Purchase #2	$200.83	10.458%	$221.8328	$221.83	$221.85	$221.80
Purchase #3	$131.56	11.599%	$146.8196	$146.82	$146.80	$146.80
Purchase #4	$64.82	9.662%	$71.0829	$71.08	$71.10	$71.10
Purchase #5	$225.41	6.433%	$239.9106	$239.91	$239.90	$239.90
Purchase #6	$184.63	3.489%	$191.0717	$191.07	$191.05	$191.10
Purchase #7	$70.55	11.490%	$78.6562	$78.66	$78.65	$78.70
7 purchase totals =	$1,086.77		$1,186.3437	$1,186.34	$1,186.30	$1,186.40