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	$35.35	5.668%	$37.3536	$37.35	$37.35	$37.40
Purchase #2	$156.86	5.418%	$165.3587	$165.36	$165.35	$165.40
Purchase #3	$220.70	4.831%	$231.362	$231.36	$231.35	$231.40
Purchase #4	$156.57	9.327%	$171.1733	$171.17	$171.15	$171.20
Purchase #5	$156.80	9.798%	$172.1633	$172.16	$172.15	$172.20
Purchase #6	$172.91	13.828%	$196.82	$196.82	$196.80	$196.80
Purchase #7	$201.95	8.226%	$218.5624	$218.56	$218.55	$218.60
7 purchase totals =	$1,101.14		$1,192.7933	$1,192.78	$1,192.70	$1,193.00