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	$81.61	10.817%	$90.4378	$90.44	$90.45	$90.40
Purchase #2	$227.76	3.176%	$234.9937	$234.99	$235.00	$235.00
Purchase #3	$92.72	3.558%	$96.019	$96.02	$96.00	$96.00
Purchase #4	$250.25	9.229%	$273.3456	$273.35	$273.35	$273.30
Purchase #5	$38.58	5.344%	$40.6417	$40.64	$40.65	$40.60
Purchase #6	$173.91	7.739%	$187.3689	$187.37	$187.35	$187.40
Purchase #7	$41.31	10.188%	$45.5187	$45.52	$45.50	$45.50
7 purchase totals =	$906.14		$968.3254	$968.33	$968.30	$968.20