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	$57.58	3.744%	$59.7358	$59.74	$59.75	$59.70
Purchase #2	$96.82	12.646%	$109.0639	$109.06	$109.05	$109.10
Purchase #3	$193.90	8.780%	$210.9244	$210.92	$210.90	$210.90
Purchase #4	$38.41	13.277%	$43.5097	$43.51	$43.50	$43.50
Purchase #5	$30.52	11.377%	$33.9923	$33.99	$34.00	$34.00
Purchase #6	$156.27	11.541%	$174.3051	$174.31	$174.30	$174.30
Purchase #7	$66.95	7.555%	$72.0081	$72.01	$72.00	$72.00
7 purchase totals =	$640.45		$703.5393	$703.54	$703.50	$703.50