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	$25.69	3.385%	$26.5596	$26.56	$26.55	$26.60
Purchase #2	$82.69	8.377%	$89.6169	$89.62	$89.60	$89.60
Purchase #3	$74.45	5.459%	$78.5142	$78.51	$78.50	$78.50
Purchase #4	$195.39	8.373%	$211.75	$211.75	$211.75	$211.80
Purchase #5	$149.69	10.249%	$165.0317	$165.03	$165.05	$165.00
Purchase #6	$116.36	6.139%	$123.5033	$123.50	$123.50	$123.50
Purchase #7	$96.93	13.350%	$109.8702	$109.87	$109.85	$109.90
7 purchase totals =	$741.20		$804.8459	$804.84	$804.80	$804.90