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	$47.29	7.682%	$50.9228	$50.92	$50.90	$50.90
Purchase #2	$86.69	8.506%	$94.0639	$94.06	$94.05	$94.10
Purchase #3	$250.96	12.413%	$282.1117	$282.11	$282.10	$282.10
Purchase #4	$92.56	10.836%	$102.5898	$102.59	$102.60	$102.60
Purchase #5	$61.84	7.111%	$66.2374	$66.24	$66.25	$66.20
Purchase #6	$61.93	12.846%	$69.8855	$69.89	$69.90	$69.90
Purchase #7	$33.38	12.366%	$37.5078	$37.51	$37.50	$37.50
7 purchase totals =	$634.65		$703.3189	$703.32	$703.30	$703.30