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	$86.30	8.713%	$93.8193	$93.82	$93.80	$93.80
Purchase #2	$28.70	10.375%	$31.6776	$31.68	$31.70	$31.70
Purchase #3	$182.71	4.802%	$191.4837	$191.48	$191.50	$191.50
Purchase #4	$45.52	7.507%	$48.9372	$48.94	$48.95	$48.90
Purchase #5	$166.86	8.514%	$181.0665	$181.07	$181.05	$181.10
Purchase #6	$96.70	13.390%	$109.6481	$109.65	$109.65	$109.60
Purchase #7	$33.82	10.745%	$37.454	$37.45	$37.45	$37.50
7 purchase totals =	$640.61		$694.0864	$694.09	$694.10	$694.10