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	$146.27	4.799%	$153.2895	$153.29	$153.30	$153.30
Purchase #2	$61.64	4.535%	$64.4354	$64.44	$64.45	$64.40
Purchase #3	$105.52	11.406%	$117.5556	$117.56	$117.55	$117.60
Purchase #4	$175.32	9.868%	$192.6206	$192.62	$192.60	$192.60
Purchase #5	$168.62	6.481%	$179.5483	$179.55	$179.55	$179.50
Purchase #6	$156.36	6.759%	$166.9284	$166.93	$166.95	$166.90
Purchase #7	$51.58	10.295%	$56.8902	$56.89	$56.90	$56.90
7 purchase totals =	$865.31		$931.2680	$931.28	$931.30	$931.20