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	$176.95	12.309%	$198.7308	$198.73	$198.75	$198.70
Purchase #2	$246.67	10.794%	$273.2956	$273.30	$273.30	$273.30
Purchase #3	$228.53	5.791%	$241.7642	$241.76	$241.75	$241.80
Purchase #4	$54.34	9.402%	$59.449	$59.45	$59.45	$59.40
Purchase #5	$68.73	4.122%	$71.5631	$71.56	$71.55	$71.60
Purchase #6	$52.51	7.107%	$56.2419	$56.24	$56.25	$56.20
Purchase #7	$158.44	4.422%	$165.4462	$165.45	$165.45	$165.40
7 purchase totals =	$986.17		$1,066.4908	$1,066.49	$1,066.50	$1,066.40