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	$34.43	11.251%	$38.3037	$38.30	$38.30	$38.30
Purchase #2	$222.59	7.394%	$239.0483	$239.05	$239.05	$239.00
Purchase #3	$43.93	3.191%	$45.3318	$45.33	$45.35	$45.30
Purchase #4	$185.64	13.240%	$210.2187	$210.22	$210.20	$210.20
Purchase #5	$136.79	10.120%	$150.6331	$150.63	$150.65	$150.60
Purchase #6	$153.76	5.628%	$162.4136	$162.41	$162.40	$162.40
Purchase #7	$244.64	10.509%	$270.3492	$270.35	$270.35	$270.30
7 purchase totals =	$1,021.78		$1,116.2984	$1,116.29	$1,116.30	$1,116.10