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	$87.99	5.270%	$92.6271	$92.63	$92.65	$92.60
Purchase #2	$25.97	10.257%	$28.6337	$28.63	$28.65	$28.60
Purchase #3	$124.53	13.608%	$141.476	$141.48	$141.50	$141.50
Purchase #4	$43.61	3.293%	$45.0461	$45.05	$45.05	$45.00
Purchase #5	$60.53	3.207%	$62.4712	$62.47	$62.45	$62.50
Purchase #6	$187.93	4.381%	$196.1632	$196.16	$196.15	$196.20
Purchase #7	$209.56	11.712%	$234.1037	$234.10	$234.10	$234.10
7 purchase totals =	$740.12		$800.5210	$800.52	$800.55	$800.50