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	$110.99	5.486%	$117.0789	$117.08	$117.10	$117.10
Purchase #2	$144.42	12.596%	$162.6111	$162.61	$162.60	$162.60
Purchase #3	$97.27	6.302%	$103.4	$103.40	$103.40	$103.40
Purchase #4	$129.52	13.550%	$147.07	$147.07	$147.05	$147.10
Purchase #5	$134.89	5.708%	$142.5895	$142.59	$142.60	$142.60
Purchase #6	$67.91	7.225%	$72.8165	$72.82	$72.80	$72.80
Purchase #7	$8.91	13.397%	$10.1037	$10.10	$10.10	$10.10
7 purchase totals =	$693.91		$755.6697	$755.67	$755.65	$755.70