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	$35.60	4.637%	$37.2508	$37.25	$37.25	$37.30
Purchase #2	$64.46	3.734%	$66.8669	$66.87	$66.85	$66.90
Purchase #3	$64.55	7.418%	$69.3383	$69.34	$69.35	$69.30
Purchase #4	$97.33	6.738%	$103.8881	$103.89	$103.90	$103.90
Purchase #5	$82.44	13.345%	$93.4416	$93.44	$93.45	$93.40
Purchase #6	$169.77	9.234%	$185.4466	$185.45	$185.45	$185.40
Purchase #7	$98.70	10.643%	$109.2046	$109.20	$109.20	$109.20
7 purchase totals =	$612.85		$665.4369	$665.44	$665.45	$665.40