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	$126.88	7.701%	$136.651	$136.65	$136.65	$136.70
Purchase #2	$59.34	4.349%	$61.9207	$61.92	$61.90	$61.90
Purchase #3	$179.72	10.222%	$198.091	$198.09	$198.10	$198.10
Purchase #4	$235.37	8.186%	$254.6374	$254.64	$254.65	$254.60
Purchase #5	$101.40	6.837%	$108.3327	$108.33	$108.35	$108.30
Purchase #6	$76.26	13.572%	$86.61	$86.61	$86.60	$86.60
Purchase #7	$145.92	9.170%	$159.3009	$159.30	$159.30	$159.30
7 purchase totals =	$924.89		$1,005.5437	$1,005.54	$1,005.55	$1,005.50