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	$81.50	4.846%	$85.4495	$85.45	$85.45	$85.40
Purchase #2	$134.59	12.694%	$151.6749	$151.67	$151.65	$151.70
Purchase #3	$49.48	11.842%	$55.3394	$55.34	$55.35	$55.30
Purchase #4	$28.44	13.409%	$32.2535	$32.25	$32.25	$32.30
Purchase #5	$155.38	5.843%	$164.4589	$164.46	$164.45	$164.50
Purchase #6	$165.41	12.569%	$186.2004	$186.20	$186.20	$186.20
Purchase #7	$225.47	11.218%	$250.7632	$250.76	$250.75	$250.80
7 purchase totals =	$840.27		$926.1398	$926.13	$926.10	$926.20