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	$9.88	5.232%	$10.3969	$10.40	$10.40	$10.40
Purchase #2	$165.89	13.361%	$188.0546	$188.05	$188.05	$188.10
Purchase #3	$157.74	10.619%	$174.4904	$174.49	$174.50	$174.50
Purchase #4	$171.97	12.784%	$193.9546	$193.95	$193.95	$194.00
Purchase #5	$35.84	13.242%	$40.5859	$40.59	$40.60	$40.60
Purchase #6	$244.27	7.437%	$262.4364	$262.44	$262.45	$262.40
Purchase #7	$70.95	10.680%	$78.5275	$78.53	$78.55	$78.50
7 purchase totals =	$856.54		$948.4463	$948.45	$948.50	$948.50