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	$98.88	13.757%	$112.4829	$112.48	$112.50	$112.50
Purchase #2	$123.81	5.240%	$130.2976	$130.30	$130.30	$130.30
Purchase #3	$156.86	7.243%	$168.2214	$168.22	$168.20	$168.20
Purchase #4	$31.27	12.654%	$35.2269	$35.23	$35.25	$35.20
Purchase #5	$219.36	8.135%	$237.2049	$237.20	$237.20	$237.20
Purchase #6	$145.60	4.500%	$152.152	$152.15	$152.15	$152.20
Purchase #7	$55.78	6.720%	$59.5284	$59.53	$59.55	$59.50
7 purchase totals =	$831.56		$895.1141	$895.11	$895.15	$895.10