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	$162.89	9.428%	$178.2473	$178.25	$178.25	$178.20
Purchase #2	$19.62	3.320%	$20.2714	$20.27	$20.25	$20.30
Purchase #3	$145.52	8.374%	$157.7058	$157.71	$157.70	$157.70
Purchase #4	$54.37	11.277%	$60.5013	$60.50	$60.50	$60.50
Purchase #5	$150.30	3.708%	$155.8731	$155.87	$155.85	$155.90
Purchase #6	$141.58	11.833%	$158.3332	$158.33	$158.35	$158.30
Purchase #7	$196.44	10.665%	$217.3903	$217.39	$217.40	$217.40
7 purchase totals =	$870.72		$948.3224	$948.32	$948.30	$948.30