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	$104.97	10.179%	$115.6549	$115.65	$115.65	$115.70
Purchase #2	$127.74	6.842%	$136.48	$136.48	$136.50	$136.50
Purchase #3	$227.35	11.469%	$253.4248	$253.42	$253.40	$253.40
Purchase #4	$140.81	11.104%	$156.4455	$156.45	$156.45	$156.40
Purchase #5	$228.93	3.229%	$236.3221	$236.32	$236.30	$236.30
Purchase #6	$87.90	3.198%	$90.711	$90.71	$90.70	$90.70
Purchase #7	$146.95	6.250%	$156.1344	$156.13	$156.15	$156.10
7 purchase totals =	$1,064.65		$1,145.1727	$1,145.16	$1,145.15	$1,145.10