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	$38.96	10.601%	$43.0901	$43.09	$43.10	$43.10
Purchase #2	$98.30	10.382%	$108.5055	$108.51	$108.50	$108.50
Purchase #3	$87.29	10.728%	$96.6545	$96.65	$96.65	$96.70
Purchase #4	$190.45	13.779%	$216.6921	$216.69	$216.70	$216.70
Purchase #5	$91.80	4.623%	$96.0439	$96.04	$96.05	$96.00
Purchase #6	$38.71	6.535%	$41.2397	$41.24	$41.25	$41.20
Purchase #7	$86.76	13.258%	$98.2626	$98.26	$98.25	$98.30
7 purchase totals =	$632.27		$700.4884	$700.48	$700.50	$700.50