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	$161.49	11.809%	$180.5604	$180.56	$180.55	$180.60
Purchase #2	$85.54	11.185%	$95.1076	$95.11	$95.10	$95.10
Purchase #3	$142.33	5.834%	$150.6335	$150.63	$150.65	$150.60
Purchase #4	$18.54	12.840%	$20.9205	$20.92	$20.90	$20.90
Purchase #5	$167.74	6.364%	$178.415	$178.42	$178.40	$178.40
Purchase #6	$217.48	3.581%	$225.268	$225.27	$225.25	$225.30
Purchase #7	$248.54	6.792%	$265.4208	$265.42	$265.40	$265.40
7 purchase totals =	$1,041.66		$1,116.3258	$1,116.33	$1,116.25	$1,116.30