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	$128.88	12.551%	$145.0557	$145.06	$145.05	$145.10
Purchase #2	$168.30	10.164%	$185.406	$185.41	$185.40	$185.40
Purchase #3	$111.99	7.730%	$120.6468	$120.65	$120.65	$120.60
Purchase #4	$31.50	11.248%	$35.0431	$35.04	$35.05	$35.00
Purchase #5	$20.60	4.827%	$21.5944	$21.59	$21.60	$21.60
Purchase #6	$38.27	10.804%	$42.4047	$42.40	$42.40	$42.40
Purchase #7	$68.95	6.623%	$73.5166	$73.52	$73.50	$73.50
7 purchase totals =	$568.49		$623.6673	$623.67	$623.65	$623.60