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	$205.78	11.730%	$229.918	$229.92	$229.90	$229.90
Purchase #2	$222.28	8.161%	$240.4203	$240.42	$240.40	$240.40
Purchase #3	$154.54	13.555%	$175.4879	$175.49	$175.50	$175.50
Purchase #4	$9.73	10.674%	$10.7686	$10.77	$10.75	$10.80
Purchase #5	$152.91	12.397%	$171.8663	$171.87	$171.85	$171.90
Purchase #6	$152.93	9.398%	$167.3024	$167.30	$167.30	$167.30
Purchase #7	$89.59	13.604%	$101.7778	$101.78	$101.80	$101.80
7 purchase totals =	$987.76		$1,097.5413	$1,097.55	$1,097.50	$1,097.60