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	$164.29	10.420%	$181.409	$181.41	$181.40	$181.40
Purchase #2	$236.94	13.381%	$268.6449	$268.64	$268.65	$268.60
Purchase #3	$37.86	7.134%	$40.5609	$40.56	$40.55	$40.60
Purchase #4	$85.96	8.573%	$93.3294	$93.33	$93.35	$93.30
Purchase #5	$225.56	6.390%	$239.9733	$239.97	$239.95	$240.00
Purchase #6	$144.89	13.764%	$164.8327	$164.83	$164.85	$164.80
Purchase #7	$63.80	12.705%	$71.9058	$71.91	$71.90	$71.90
7 purchase totals =	$959.30		$1,060.6560	$1,060.65	$1,060.65	$1,060.60