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	$89.69	11.387%	$99.903	$99.90	$99.90	$99.90
Purchase #2	$45.51	4.629%	$47.6167	$47.62	$47.60	$47.60
Purchase #3	$100.66	8.494%	$109.2101	$109.21	$109.20	$109.20
Purchase #4	$86.38	3.276%	$89.2098	$89.21	$89.20	$89.20
Purchase #5	$184.26	4.145%	$191.8976	$191.90	$191.90	$191.90
Purchase #6	$246.60	9.471%	$269.9555	$269.96	$269.95	$270.00
Purchase #7	$227.58	5.640%	$240.4155	$240.42	$240.40	$240.40
7 purchase totals =	$980.68		$1,048.2082	$1,048.22	$1,048.15	$1,048.20