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	$237.49	7.315%	$254.8624	$254.86	$254.85	$254.90
Purchase #2	$198.26	4.147%	$206.4818	$206.48	$206.50	$206.50
Purchase #3	$239.92	10.244%	$264.4974	$264.50	$264.50	$264.50
Purchase #4	$72.98	12.792%	$82.3156	$82.32	$82.30	$82.30
Purchase #5	$133.47	7.330%	$143.2534	$143.25	$143.25	$143.30
Purchase #6	$131.84	7.524%	$141.7596	$141.76	$141.75	$141.80
Purchase #7	$96.32	11.695%	$107.5846	$107.58	$107.60	$107.60
7 purchase totals =	$1,110.28		$1,200.7548	$1,200.75	$1,200.75	$1,200.90