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	$132.81	7.182%	$142.3484	$142.35	$142.35	$142.30
Purchase #2	$119.41	6.676%	$127.3818	$127.38	$127.40	$127.40
Purchase #3	$213.31	4.544%	$223.0028	$223.00	$223.00	$223.00
Purchase #4	$112.34	13.364%	$127.3531	$127.35	$127.35	$127.40
Purchase #5	$189.61	3.784%	$196.7848	$196.78	$196.80	$196.80
Purchase #6	$100.87	12.623%	$113.6028	$113.60	$113.60	$113.60
Purchase #7	$34.88	11.557%	$38.9111	$38.91	$38.90	$38.90
7 purchase totals =	$903.23		$969.3848	$969.37	$969.40	$969.40