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	$103.80	9.192%	$113.3413	$113.34	$113.35	$113.30
Purchase #2	$147.52	11.824%	$164.9628	$164.96	$164.95	$165.00
Purchase #3	$152.57	5.549%	$161.0361	$161.04	$161.05	$161.00
Purchase #4	$142.59	12.396%	$160.2655	$160.27	$160.25	$160.30
Purchase #5	$236.66	5.170%	$248.8953	$248.90	$248.90	$248.90
Purchase #6	$64.86	10.242%	$71.503	$71.50	$71.50	$71.50
Purchase #7	$229.42	13.271%	$259.8663	$259.87	$259.85	$259.90
7 purchase totals =	$1,077.42		$1,179.8703	$1,179.88	$1,179.85	$1,179.90