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	$82.36	4.485%	$86.0538	$86.05	$86.05	$86.10
Purchase #2	$150.83	12.622%	$169.8678	$169.87	$169.85	$169.90
Purchase #3	$128.79	12.712%	$145.1618	$145.16	$145.15	$145.20
Purchase #4	$80.94	10.324%	$89.2962	$89.30	$89.30	$89.30
Purchase #5	$40.31	8.320%	$43.6638	$43.66	$43.65	$43.70
Purchase #6	$82.46	12.123%	$92.4566	$92.46	$92.45	$92.50
Purchase #7	$142.63	11.418%	$158.9155	$158.92	$158.90	$158.90
7 purchase totals =	$708.32		$785.4155	$785.42	$785.35	$785.60