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	$244.29	6.675%	$260.5964	$260.60	$260.60	$260.60
Purchase #2	$131.78	7.319%	$141.425	$141.43	$141.45	$141.40
Purchase #3	$190.42	10.311%	$210.0542	$210.05	$210.05	$210.10
Purchase #4	$107.27	10.351%	$118.3735	$118.37	$118.35	$118.40
Purchase #5	$134.73	7.761%	$145.1864	$145.19	$145.20	$145.20
Purchase #6	$95.99	3.822%	$99.6587	$99.66	$99.65	$99.70
Purchase #7	$82.32	11.218%	$91.5547	$91.55	$91.55	$91.60
7 purchase totals =	$986.80		$1,066.8489	$1,066.85	$1,066.85	$1,067.00