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	$211.73	12.216%	$237.5949	$237.59	$237.60	$237.60
Purchase #2	$181.35	4.201%	$188.9685	$188.97	$188.95	$189.00
Purchase #3	$215.64	3.567%	$223.3319	$223.33	$223.35	$223.30
Purchase #4	$129.84	12.129%	$145.5883	$145.59	$145.60	$145.60
Purchase #5	$143.56	8.170%	$155.2889	$155.29	$155.30	$155.30
Purchase #6	$74.55	5.804%	$78.8769	$78.88	$78.90	$78.90
Purchase #7	$159.31	6.240%	$169.2509	$169.25	$169.25	$169.30
7 purchase totals =	$1,115.98		$1,198.9003	$1,198.90	$1,198.95	$1,199.00