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	$100.87	10.348%	$111.308	$111.31	$111.30	$111.30
Purchase #2	$129.41	7.165%	$138.6822	$138.68	$138.70	$138.70
Purchase #3	$105.44	5.143%	$110.8628	$110.86	$110.85	$110.90
Purchase #4	$136.85	10.837%	$151.6804	$151.68	$151.70	$151.70
Purchase #5	$213.98	10.469%	$236.3816	$236.38	$236.40	$236.40
Purchase #6	$194.73	10.696%	$215.5583	$215.56	$215.55	$215.60
Purchase #7	$80.50	12.202%	$90.3226	$90.32	$90.30	$90.30
7 purchase totals =	$961.78		$1,054.7959	$1,054.79	$1,054.80	$1,054.90