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	$114.81	7.374%	$123.2761	$123.28	$123.30	$123.30
Purchase #2	$76.97	7.678%	$82.8798	$82.88	$82.90	$82.90
Purchase #3	$35.46	5.447%	$37.3915	$37.39	$37.40	$37.40
Purchase #4	$43.57	9.109%	$47.5388	$47.54	$47.55	$47.50
Purchase #5	$59.85	6.759%	$63.8953	$63.90	$63.90	$63.90
Purchase #6	$214.84	9.695%	$235.6687	$235.67	$235.65	$235.70
Purchase #7	$214.72	13.593%	$243.9069	$243.91	$243.90	$243.90
7 purchase totals =	$760.22		$834.5571	$834.57	$834.60	$834.60