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	$210.56	8.561%	$228.586	$228.59	$228.60	$228.60
Purchase #2	$168.76	13.374%	$191.33	$191.33	$191.35	$191.30
Purchase #3	$249.70	10.475%	$275.8561	$275.86	$275.85	$275.90
Purchase #4	$17.92	6.383%	$19.0638	$19.06	$19.05	$19.10
Purchase #5	$144.65	7.185%	$155.0431	$155.04	$155.05	$155.00
Purchase #6	$74.74	7.665%	$80.4688	$80.47	$80.45	$80.50
Purchase #7	$98.65	5.617%	$104.1912	$104.19	$104.20	$104.20
7 purchase totals =	$964.98		$1,054.5390	$1,054.54	$1,054.55	$1,054.60