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	$158.37	9.317%	$173.1253	$173.13	$173.15	$173.10
Purchase #2	$241.85	7.284%	$259.4664	$259.47	$259.45	$259.50
Purchase #3	$227.77	9.136%	$248.5791	$248.58	$248.60	$248.60
Purchase #4	$173.63	10.368%	$191.632	$191.63	$191.65	$191.60
Purchase #5	$116.68	11.169%	$129.712	$129.71	$129.70	$129.70
Purchase #6	$53.87	11.238%	$59.9239	$59.92	$59.90	$59.90
Purchase #7	$79.70	7.166%	$85.4113	$85.41	$85.40	$85.40
7 purchase totals =	$1,051.87		$1,147.8500	$1,147.85	$1,147.85	$1,147.80