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	$158.32	8.743%	$172.1619	$172.16	$172.15	$172.20
Purchase #2	$28.51	10.250%	$31.4323	$31.43	$31.45	$31.40
Purchase #3	$132.45	11.686%	$147.9281	$147.93	$147.95	$147.90
Purchase #4	$162.96	12.684%	$183.6298	$183.63	$183.65	$183.60
Purchase #5	$168.78	11.560%	$188.291	$188.29	$188.30	$188.30
Purchase #6	$46.87	10.192%	$51.647	$51.65	$51.65	$51.60
Purchase #7	$165.27	8.592%	$179.47	$179.47	$179.45	$179.50
7 purchase totals =	$863.16		$954.5601	$954.56	$954.60	$954.50