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	$198.75	13.789%	$226.1556	$226.16	$226.15	$226.20
Purchase #2	$128.39	8.354%	$139.1157	$139.12	$139.10	$139.10
Purchase #3	$162.27	7.465%	$174.3835	$174.38	$174.40	$174.40
Purchase #4	$69.26	12.846%	$78.1571	$78.16	$78.15	$78.20
Purchase #5	$172.55	5.407%	$181.8798	$181.88	$181.90	$181.90
Purchase #6	$43.52	13.697%	$49.4809	$49.48	$49.50	$49.50
Purchase #7	$153.98	7.499%	$165.527	$165.53	$165.55	$165.50
7 purchase totals =	$928.72		$1,014.6996	$1,014.71	$1,014.75	$1,014.80