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	$231.27	5.430%	$243.828	$243.83	$243.85	$243.80
Purchase #2	$145.73	6.677%	$155.4604	$155.46	$155.45	$155.50
Purchase #3	$224.31	8.463%	$243.2934	$243.29	$243.30	$243.30
Purchase #4	$229.93	3.390%	$237.7246	$237.72	$237.70	$237.70
Purchase #5	$34.71	13.658%	$39.4507	$39.45	$39.45	$39.50
Purchase #6	$234.33	3.491%	$242.5105	$242.51	$242.50	$242.50
Purchase #7	$142.95	6.409%	$152.1117	$152.11	$152.10	$152.10
7 purchase totals =	$1,243.23		$1,314.3793	$1,314.37	$1,314.35	$1,314.40