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	$108.33	3.170%	$111.7641	$111.76	$111.75	$111.80
Purchase #2	$237.39	9.302%	$259.472	$259.47	$259.45	$259.50
Purchase #3	$171.38	5.806%	$181.3303	$181.33	$181.35	$181.30
Purchase #4	$74.89	12.851%	$84.5141	$84.51	$84.50	$84.50
Purchase #5	$71.54	12.499%	$80.4818	$80.48	$80.50	$80.50
Purchase #6	$213.91	10.238%	$235.8101	$235.81	$235.80	$235.80
Purchase #7	$134.42	3.498%	$139.122	$139.12	$139.10	$139.10
7 purchase totals =	$1,011.86		$1,092.4944	$1,092.48	$1,092.45	$1,092.50