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	$136.76	11.787%	$152.8799	$152.88	$152.90	$152.90
Purchase #2	$41.39	10.254%	$45.6341	$45.63	$45.65	$45.60
Purchase #3	$36.41	8.345%	$39.4484	$39.45	$39.45	$39.40
Purchase #4	$234.72	12.665%	$264.4473	$264.45	$264.45	$264.40
Purchase #5	$164.90	9.636%	$180.7898	$180.79	$180.80	$180.80
Purchase #6	$112.52	12.768%	$126.8866	$126.89	$126.90	$126.90
Purchase #7	$39.48	10.365%	$43.5721	$43.57	$43.55	$43.60
7 purchase totals =	$766.18		$853.6582	$853.66	$853.70	$853.60