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	$79.55	9.223%	$86.8869	$86.89	$86.90	$86.90
Purchase #2	$104.56	4.798%	$109.5768	$109.58	$109.60	$109.60
Purchase #3	$142.91	13.853%	$162.7073	$162.71	$162.70	$162.70
Purchase #4	$51.79	3.462%	$53.583	$53.58	$53.60	$53.60
Purchase #5	$86.84	13.185%	$98.2899	$98.29	$98.30	$98.30
Purchase #6	$100.90	9.363%	$110.3473	$110.35	$110.35	$110.30
Purchase #7	$222.77	7.559%	$239.6092	$239.61	$239.60	$239.60
7 purchase totals =	$789.32		$861.0004	$861.01	$861.05	$861.00