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	$118.65	6.305%	$126.1309	$126.13	$126.15	$126.10
Purchase #2	$89.31	11.128%	$99.2484	$99.25	$99.25	$99.20
Purchase #3	$73.28	9.407%	$80.1734	$80.17	$80.15	$80.20
Purchase #4	$216.44	6.142%	$229.7337	$229.73	$229.75	$229.70
Purchase #5	$116.95	9.826%	$128.4415	$128.44	$128.45	$128.40
Purchase #6	$151.56	8.402%	$164.2941	$164.29	$164.30	$164.30
Purchase #7	$155.35	10.828%	$172.1713	$172.17	$172.15	$172.20
7 purchase totals =	$921.54		$1,000.1933	$1,000.18	$1,000.20	$1,000.10