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	$180.38	3.541%	$186.7673	$186.77	$186.75	$186.80
Purchase #2	$60.31	11.424%	$67.1998	$67.20	$67.20	$67.20
Purchase #3	$148.34	3.517%	$153.5571	$153.56	$153.55	$153.60
Purchase #4	$19.52	10.464%	$21.5626	$21.56	$21.55	$21.60
Purchase #5	$246.40	7.345%	$264.4981	$264.50	$264.50	$264.50
Purchase #6	$40.34	7.334%	$43.2985	$43.30	$43.30	$43.30
Purchase #7	$95.54	5.443%	$100.7402	$100.74	$100.75	$100.70
7 purchase totals =	$790.83		$837.6236	$837.63	$837.60	$837.70