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	$41.28	6.535%	$43.9776	$43.98	$44.00	$44.00
Purchase #2	$220.63	13.362%	$250.1106	$250.11	$250.10	$250.10
Purchase #3	$243.38	8.681%	$264.5078	$264.51	$264.50	$264.50
Purchase #4	$16.90	9.681%	$18.5361	$18.54	$18.55	$18.50
Purchase #5	$44.33	6.398%	$47.1662	$47.17	$47.15	$47.20
Purchase #6	$10.83	9.209%	$11.8273	$11.83	$11.85	$11.80
Purchase #7	$186.45	3.146%	$192.3157	$192.32	$192.30	$192.30
7 purchase totals =	$763.80		$828.4413	$828.46	$828.45	$828.40