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	$173.77	4.199%	$181.0666	$181.07	$181.05	$181.10
Purchase #2	$7.27	3.436%	$7.5198	$7.52	$7.50	$7.50
Purchase #3	$248.48	12.475%	$279.4779	$279.48	$279.50	$279.50
Purchase #4	$64.78	10.848%	$71.8073	$71.81	$71.80	$71.80
Purchase #5	$34.45	10.720%	$38.143	$38.14	$38.15	$38.10
Purchase #6	$92.25	8.621%	$100.2029	$100.20	$100.20	$100.20
Purchase #7	$96.92	5.353%	$102.1081	$102.11	$102.10	$102.10
7 purchase totals =	$717.92		$780.3256	$780.33	$780.30	$780.30