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	$248.67	10.202%	$274.0393	$274.04	$274.05	$274.00
Purchase #2	$67.55	5.164%	$71.0383	$71.04	$71.05	$71.00
Purchase #3	$73.85	6.656%	$78.7655	$78.77	$78.75	$78.80
Purchase #4	$79.27	9.242%	$86.5961	$86.60	$86.60	$86.60
Purchase #5	$130.55	7.725%	$140.635	$140.64	$140.65	$140.60
Purchase #6	$14.25	10.214%	$15.7055	$15.71	$15.70	$15.70
Purchase #7	$90.28	6.592%	$96.2313	$96.23	$96.25	$96.20
7 purchase totals =	$704.42		$763.0110	$763.03	$763.05	$762.90