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	$108.76	6.711%	$116.0589	$116.06	$116.05	$116.10
Purchase #2	$111.75	7.652%	$120.3011	$120.30	$120.30	$120.30
Purchase #3	$210.90	6.804%	$225.2496	$225.25	$225.25	$225.20
Purchase #4	$247.37	7.776%	$266.6055	$266.61	$266.60	$266.60
Purchase #5	$215.64	3.566%	$223.3297	$223.33	$223.35	$223.30
Purchase #6	$102.59	9.452%	$112.2868	$112.29	$112.30	$112.30
Purchase #7	$81.89	7.771%	$88.2537	$88.25	$88.25	$88.30
7 purchase totals =	$1,078.90		$1,152.0853	$1,152.09	$1,152.10	$1,152.10