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	$236.59	7.613%	$254.6016	$254.60	$254.60	$254.60
Purchase #2	$44.55	5.307%	$46.9143	$46.91	$46.90	$46.90
Purchase #3	$92.56	5.352%	$97.5138	$97.51	$97.50	$97.50
Purchase #4	$184.81	3.841%	$191.9086	$191.91	$191.90	$191.90
Purchase #5	$171.77	12.149%	$192.6383	$192.64	$192.65	$192.60
Purchase #6	$85.38	13.478%	$96.8875	$96.89	$96.90	$96.90
Purchase #7	$96.53	6.140%	$102.4569	$102.46	$102.45	$102.50
7 purchase totals =	$912.19		$982.9210	$982.92	$982.90	$982.90