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	$109.52	4.221%	$114.1428	$114.14	$114.15	$114.10
Purchase #2	$32.42	3.528%	$33.5638	$33.56	$33.55	$33.60
Purchase #3	$93.86	9.754%	$103.0151	$103.02	$103.00	$103.00
Purchase #4	$119.37	3.237%	$123.234	$123.23	$123.25	$123.20
Purchase #5	$83.36	5.103%	$87.6139	$87.61	$87.60	$87.60
Purchase #6	$178.81	4.370%	$186.624	$186.62	$186.60	$186.60
Purchase #7	$46.46	6.179%	$49.3308	$49.33	$49.35	$49.30
7 purchase totals =	$663.80		$697.5244	$697.51	$697.50	$697.40