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	$175.96	11.665%	$196.4857	$196.49	$196.50	$196.50
Purchase #2	$150.79	11.308%	$167.8413	$167.84	$167.85	$167.80
Purchase #3	$91.96	6.684%	$98.1066	$98.11	$98.10	$98.10
Purchase #4	$93.57	6.673%	$99.8139	$99.81	$99.80	$99.80
Purchase #5	$74.98	11.321%	$83.4685	$83.47	$83.45	$83.50
Purchase #6	$78.25	5.531%	$82.578	$82.58	$82.60	$82.60
Purchase #7	$21.32	9.242%	$23.2904	$23.29	$23.30	$23.30
7 purchase totals =	$686.83		$751.5844	$751.59	$751.60	$751.60