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	$157.44	3.194%	$162.4686	$162.47	$162.45	$162.50
Purchase #2	$122.83	5.465%	$129.5427	$129.54	$129.55	$129.50
Purchase #3	$128.84	12.780%	$145.3058	$145.31	$145.30	$145.30
Purchase #4	$132.41	12.529%	$148.9996	$149.00	$149.00	$149.00
Purchase #5	$68.76	5.599%	$72.6099	$72.61	$72.60	$72.60
Purchase #6	$19.51	7.337%	$20.9414	$20.94	$20.95	$20.90
Purchase #7	$39.92	6.740%	$42.6106	$42.61	$42.60	$42.60
7 purchase totals =	$669.71		$722.4786	$722.48	$722.45	$722.40