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	$114.80	7.556%	$123.4743	$123.47	$123.45	$123.50
Purchase #2	$165.31	10.372%	$182.456	$182.46	$182.45	$182.50
Purchase #3	$138.65	12.552%	$156.0533	$156.05	$156.05	$156.10
Purchase #4	$191.50	13.371%	$217.1055	$217.11	$217.10	$217.10
Purchase #5	$150.39	13.850%	$171.219	$171.22	$171.20	$171.20
Purchase #6	$54.38	8.391%	$58.943	$58.94	$58.95	$58.90
Purchase #7	$59.46	3.187%	$61.355	$61.36	$61.35	$61.40
7 purchase totals =	$874.49		$970.6061	$970.61	$970.55	$970.70