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	$29.73	8.808%	$32.3486	$32.35	$32.35	$32.30
Purchase #2	$204.46	13.321%	$231.6961	$231.70	$231.70	$231.70
Purchase #3	$113.78	3.848%	$118.1583	$118.16	$118.15	$118.20
Purchase #4	$26.65	3.539%	$27.5931	$27.59	$27.60	$27.60
Purchase #5	$248.34	6.471%	$264.4101	$264.41	$264.40	$264.40
Purchase #6	$54.90	9.111%	$59.9019	$59.90	$59.90	$59.90
Purchase #7	$231.38	6.129%	$245.5613	$245.56	$245.55	$245.60
7 purchase totals =	$909.24		$979.6694	$979.67	$979.65	$979.70