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	$234.62	7.623%	$252.5051	$252.51	$252.50	$252.50
Purchase #2	$171.61	8.546%	$186.2758	$186.28	$186.30	$186.30
Purchase #3	$162.77	13.571%	$184.8595	$184.86	$184.85	$184.90
Purchase #4	$69.62	12.192%	$78.1081	$78.11	$78.10	$78.10
Purchase #5	$160.55	6.798%	$171.4642	$171.46	$171.45	$171.50
Purchase #6	$82.68	7.871%	$89.1877	$89.19	$89.20	$89.20
Purchase #7	$182.96	12.184%	$205.2518	$205.25	$205.25	$205.30
7 purchase totals =	$1,064.81		$1,167.6522	$1,167.66	$1,167.65	$1,167.80