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	$206.62	10.533%	$228.3833	$228.38	$228.40	$228.40
Purchase #2	$90.88	11.479%	$101.3121	$101.31	$101.30	$101.30
Purchase #3	$103.38	5.152%	$108.7061	$108.71	$108.70	$108.70
Purchase #4	$225.31	12.687%	$253.8951	$253.90	$253.90	$253.90
Purchase #5	$181.28	8.324%	$196.3697	$196.37	$196.35	$196.40
Purchase #6	$37.39	7.631%	$40.2432	$40.24	$40.25	$40.20
Purchase #7	$28.30	11.859%	$31.6561	$31.66	$31.65	$31.70
7 purchase totals =	$873.16		$960.5656	$960.57	$960.55	$960.60