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	$72.49	13.536%	$82.3022	$82.30	$82.30	$82.30
Purchase #2	$163.84	6.183%	$173.9702	$173.97	$173.95	$174.00
Purchase #3	$134.50	13.398%	$152.5203	$152.52	$152.50	$152.50
Purchase #4	$229.91	6.805%	$245.5554	$245.56	$245.55	$245.60
Purchase #5	$147.61	5.199%	$155.2842	$155.28	$155.30	$155.30
Purchase #6	$78.61	13.258%	$89.0321	$89.03	$89.05	$89.00
Purchase #7	$58.70	3.254%	$60.6101	$60.61	$60.60	$60.60
7 purchase totals =	$885.66		$959.2745	$959.27	$959.25	$959.30