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	$184.79	6.116%	$196.0918	$196.09	$196.10	$196.10
Purchase #2	$141.44	4.358%	$147.604	$147.60	$147.60	$147.60
Purchase #3	$82.81	11.142%	$92.0367	$92.04	$92.05	$92.00
Purchase #4	$216.52	8.709%	$235.3767	$235.38	$235.40	$235.40
Purchase #5	$165.78	10.157%	$182.6183	$182.62	$182.60	$182.60
Purchase #6	$245.31	12.268%	$275.4046	$275.40	$275.40	$275.40
Purchase #7	$167.35	3.317%	$172.901	$172.90	$172.90	$172.90
7 purchase totals =	$1,204.00		$1,302.0331	$1,302.03	$1,302.05	$1,302.00