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	$141.34	5.348%	$148.8989	$148.90	$148.90	$148.90
Purchase #2	$58.58	6.383%	$62.3192	$62.32	$62.30	$62.30
Purchase #3	$94.38	5.871%	$99.921	$99.92	$99.90	$99.90
Purchase #4	$53.93	11.120%	$59.927	$59.93	$59.95	$59.90
Purchase #5	$166.71	11.791%	$186.3668	$186.37	$186.35	$186.40
Purchase #6	$110.75	11.227%	$123.1839	$123.18	$123.20	$123.20
Purchase #7	$187.95	3.460%	$194.4531	$194.45	$194.45	$194.50
7 purchase totals =	$813.64		$875.0699	$875.07	$875.05	$875.10