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	$141.33	4.859%	$148.1972	$148.20	$148.20	$148.20
Purchase #2	$109.92	7.613%	$118.2882	$118.29	$118.30	$118.30
Purchase #3	$64.63	9.156%	$70.5475	$70.55	$70.55	$70.50
Purchase #4	$54.77	8.523%	$59.438	$59.44	$59.45	$59.40
Purchase #5	$38.74	5.596%	$40.9079	$40.91	$40.90	$40.90
Purchase #6	$110.59	13.832%	$125.8868	$125.89	$125.90	$125.90
Purchase #7	$196.33	11.511%	$218.9295	$218.93	$218.95	$218.90
7 purchase totals =	$716.31		$782.1951	$782.21	$782.25	$782.10