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	$186.43	13.334%	$211.2886	$211.29	$211.30	$211.30
Purchase #2	$71.43	3.596%	$73.9986	$74.00	$74.00	$74.00
Purchase #3	$208.54	6.694%	$222.4997	$222.50	$222.50	$222.50
Purchase #4	$48.57	5.503%	$51.2428	$51.24	$51.25	$51.20
Purchase #5	$184.29	6.550%	$196.361	$196.36	$196.35	$196.40
Purchase #6	$79.70	9.805%	$87.5146	$87.51	$87.50	$87.50
Purchase #7	$90.76	6.456%	$96.6195	$96.62	$96.60	$96.60
7 purchase totals =	$869.72		$939.5248	$939.52	$939.50	$939.50