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	$106.59	7.276%	$114.3455	$114.35	$114.35	$114.30
Purchase #2	$122.73	6.750%	$131.0143	$131.01	$131.00	$131.00
Purchase #3	$207.68	7.671%	$223.6111	$223.61	$223.60	$223.60
Purchase #4	$107.31	5.561%	$113.2775	$113.28	$113.30	$113.30
Purchase #5	$165.69	11.675%	$185.0343	$185.03	$185.05	$185.00
Purchase #6	$131.66	9.237%	$143.8214	$143.82	$143.80	$143.80
Purchase #7	$98.53	8.479%	$106.8844	$106.88	$106.90	$106.90
7 purchase totals =	$940.19		$1,017.9885	$1,017.98	$1,018.00	$1,017.90