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	$27.48	11.413%	$30.6163	$30.62	$30.60	$30.60
Purchase #2	$81.82	13.227%	$92.6423	$92.64	$92.65	$92.60
Purchase #3	$228.45	7.421%	$245.4033	$245.40	$245.40	$245.40
Purchase #4	$67.83	6.542%	$72.2674	$72.27	$72.25	$72.30
Purchase #5	$219.38	13.380%	$248.733	$248.73	$248.75	$248.70
Purchase #6	$225.81	6.677%	$240.8873	$240.89	$240.90	$240.90
Purchase #7	$136.55	13.269%	$154.6688	$154.67	$154.65	$154.70
7 purchase totals =	$987.32		$1,085.2184	$1,085.22	$1,085.20	$1,085.20