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	$158.40	4.119%	$164.9245	$164.92	$164.90	$164.90
Purchase #2	$80.58	10.398%	$88.9587	$88.96	$88.95	$89.00
Purchase #3	$210.94	7.124%	$225.9674	$225.97	$225.95	$226.00
Purchase #4	$17.32	5.817%	$18.3275	$18.33	$18.35	$18.30
Purchase #5	$88.30	8.802%	$96.0722	$96.07	$96.05	$96.10
Purchase #6	$99.47	13.164%	$112.5642	$112.56	$112.55	$112.60
Purchase #7	$34.32	9.734%	$37.6607	$37.66	$37.65	$37.70
7 purchase totals =	$689.33		$744.4752	$744.47	$744.40	$744.60