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	$53.67	8.747%	$58.3645	$58.36	$58.35	$58.40
Purchase #2	$15.40	8.700%	$16.7398	$16.74	$16.75	$16.70
Purchase #3	$27.90	6.688%	$29.766	$29.77	$29.75	$29.80
Purchase #4	$72.71	8.138%	$78.6271	$78.63	$78.65	$78.60
Purchase #5	$92.68	11.592%	$103.4235	$103.42	$103.40	$103.40
Purchase #6	$55.35	7.301%	$59.3911	$59.39	$59.40	$59.40
Purchase #7	$90.83	7.148%	$97.3225	$97.32	$97.30	$97.30
7 purchase totals =	$408.54		$443.6345	$443.63	$443.60	$443.60