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	$65.25	3.377%	$67.4535	$67.45	$67.45	$67.50
Purchase #2	$147.32	4.409%	$153.8153	$153.82	$153.80	$153.80
Purchase #3	$90.49	8.356%	$98.0513	$98.05	$98.05	$98.10
Purchase #4	$211.90	7.760%	$228.3434	$228.34	$228.35	$228.30
Purchase #5	$139.47	9.178%	$152.2706	$152.27	$152.25	$152.30
Purchase #6	$43.54	8.681%	$47.3197	$47.32	$47.30	$47.30
Purchase #7	$170.30	9.244%	$186.0425	$186.04	$186.05	$186.00
7 purchase totals =	$868.27		$933.2963	$933.29	$933.25	$933.30