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	$184.80	6.220%	$196.2946	$196.29	$196.30	$196.30
Purchase #2	$180.72	5.438%	$190.5476	$190.55	$190.55	$190.50
Purchase #3	$136.62	9.871%	$150.1058	$150.11	$150.10	$150.10
Purchase #4	$177.46	4.215%	$184.9399	$184.94	$184.95	$184.90
Purchase #5	$78.37	9.860%	$86.0973	$86.10	$86.10	$86.10
Purchase #6	$85.26	10.506%	$94.2174	$94.22	$94.20	$94.20
Purchase #7	$188.67	3.382%	$195.0508	$195.05	$195.05	$195.10
7 purchase totals =	$1,031.90		$1,097.2534	$1,097.26	$1,097.25	$1,097.20