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	$97.79	7.225%	$104.8553	$104.86	$104.85	$104.90
Purchase #2	$56.31	8.336%	$61.004	$61.00	$61.00	$61.00
Purchase #3	$181.52	12.670%	$204.5186	$204.52	$204.50	$204.50
Purchase #4	$81.59	4.656%	$85.3888	$85.39	$85.40	$85.40
Purchase #5	$20.59	8.704%	$22.3822	$22.38	$22.40	$22.40
Purchase #6	$145.61	13.588%	$165.3955	$165.40	$165.40	$165.40
Purchase #7	$208.91	4.354%	$218.0059	$218.01	$218.00	$218.00
7 purchase totals =	$792.32		$861.5503	$861.56	$861.55	$861.60