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	$147.54	7.547%	$158.6748	$158.67	$158.65	$158.70
Purchase #2	$173.40	7.596%	$186.5715	$186.57	$186.55	$186.60
Purchase #3	$109.84	12.778%	$123.8754	$123.88	$123.90	$123.90
Purchase #4	$42.27	3.756%	$43.8577	$43.86	$43.85	$43.90
Purchase #5	$75.92	12.686%	$85.5512	$85.55	$85.55	$85.60
Purchase #6	$106.83	10.825%	$118.3943	$118.39	$118.40	$118.40
Purchase #7	$243.74	11.705%	$272.2698	$272.27	$272.25	$272.30
7 purchase totals =	$899.54		$989.1947	$989.19	$989.15	$989.40