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	$244.59	4.506%	$255.6112	$255.61	$255.60	$255.60
Purchase #2	$106.51	4.315%	$111.1059	$111.11	$111.10	$111.10
Purchase #3	$207.27	4.500%	$216.5972	$216.60	$216.60	$216.60
Purchase #4	$98.73	5.821%	$104.4771	$104.48	$104.50	$104.50
Purchase #5	$227.46	13.511%	$258.1921	$258.19	$258.20	$258.20
Purchase #6	$248.88	6.848%	$265.9233	$265.92	$265.90	$265.90
Purchase #7	$24.40	6.465%	$25.9775	$25.98	$26.00	$26.00
7 purchase totals =	$1,157.84		$1,237.8843	$1,237.89	$1,237.90	$1,237.90