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	$186.93	13.800%	$212.7263	$212.73	$212.75	$212.70
Purchase #2	$247.99	7.407%	$266.3586	$266.36	$266.35	$266.40
Purchase #3	$37.87	13.356%	$42.9279	$42.93	$42.95	$42.90
Purchase #4	$250.35	12.752%	$282.2746	$282.27	$282.25	$282.30
Purchase #5	$110.62	11.597%	$123.4486	$123.45	$123.45	$123.40
Purchase #6	$196.43	7.669%	$211.4942	$211.49	$211.50	$211.50
Purchase #7	$24.27	12.171%	$27.2239	$27.22	$27.20	$27.20
7 purchase totals =	$1,054.46		$1,166.4541	$1,166.45	$1,166.45	$1,166.40