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	$93.95	11.690%	$104.9328	$104.93	$104.95	$104.90
Purchase #2	$31.25	4.286%	$32.5894	$32.59	$32.60	$32.60
Purchase #3	$62.92	13.764%	$71.5803	$71.58	$71.60	$71.60
Purchase #4	$86.31	6.773%	$92.1558	$92.16	$92.15	$92.20
Purchase #5	$69.45	3.331%	$71.7634	$71.76	$71.75	$71.80
Purchase #6	$175.88	5.150%	$184.9378	$184.94	$184.95	$184.90
Purchase #7	$79.25	3.555%	$82.0673	$82.07	$82.05	$82.10
7 purchase totals =	$599.01		$640.0268	$640.03	$640.05	$640.10