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	$224.88	10.740%	$249.0321	$249.03	$249.05	$249.00
Purchase #2	$164.51	6.361%	$174.9745	$174.97	$174.95	$175.00
Purchase #3	$113.38	13.453%	$128.633	$128.63	$128.65	$128.60
Purchase #4	$146.82	6.427%	$156.2561	$156.26	$156.25	$156.30
Purchase #5	$110.68	8.490%	$120.0767	$120.08	$120.10	$120.10
Purchase #6	$102.84	10.710%	$113.8542	$113.85	$113.85	$113.90
Purchase #7	$52.71	12.491%	$59.294	$59.29	$59.30	$59.30
7 purchase totals =	$915.82		$1,002.1206	$1,002.11	$1,002.15	$1,002.20