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	$152.47	7.635%	$164.1111	$164.11	$164.10	$164.10
Purchase #2	$54.30	4.849%	$56.933	$56.93	$56.95	$56.90
Purchase #3	$221.63	7.489%	$238.2279	$238.23	$238.25	$238.20
Purchase #4	$95.88	4.845%	$100.5254	$100.53	$100.55	$100.50
Purchase #5	$223.92	12.323%	$251.5137	$251.51	$251.50	$251.50
Purchase #6	$27.47	13.489%	$31.1754	$31.18	$31.20	$31.20
Purchase #7	$137.33	4.115%	$142.9811	$142.98	$143.00	$143.00
7 purchase totals =	$913.00		$985.4676	$985.47	$985.55	$985.40