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	$131.63	8.568%	$142.9081	$142.91	$142.90	$142.90
Purchase #2	$124.59	5.802%	$131.8187	$131.82	$131.80	$131.80
Purchase #3	$83.61	5.583%	$88.2779	$88.28	$88.30	$88.30
Purchase #4	$126.54	3.553%	$131.036	$131.04	$131.05	$131.00
Purchase #5	$209.73	3.633%	$217.3495	$217.35	$217.35	$217.30
Purchase #6	$74.88	3.366%	$77.4005	$77.40	$77.40	$77.40
Purchase #7	$67.96	6.439%	$72.3359	$72.34	$72.35	$72.30
7 purchase totals =	$818.94		$861.1266	$861.14	$861.15	$861.00