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	$70.66	3.544%	$73.1642	$73.16	$73.15	$73.20
Purchase #2	$185.63	12.725%	$209.2514	$209.25	$209.25	$209.30
Purchase #3	$54.83	13.213%	$62.0747	$62.07	$62.05	$62.10
Purchase #4	$186.42	7.581%	$200.5525	$200.55	$200.55	$200.60
Purchase #5	$125.61	7.700%	$135.282	$135.28	$135.30	$135.30
Purchase #6	$72.25	8.846%	$78.6412	$78.64	$78.65	$78.60
Purchase #7	$100.43	3.826%	$104.2725	$104.27	$104.25	$104.30
7 purchase totals =	$795.83		$863.2385	$863.22	$863.20	$863.40