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	$137.70	3.546%	$142.5828	$142.58	$142.60	$142.60
Purchase #2	$183.35	7.267%	$196.674	$196.67	$196.65	$196.70
Purchase #3	$160.67	13.628%	$182.5661	$182.57	$182.55	$182.60
Purchase #4	$103.88	6.334%	$110.4598	$110.46	$110.45	$110.50
Purchase #5	$117.59	10.553%	$129.9993	$130.00	$130.00	$130.00
Purchase #6	$110.37	11.713%	$123.2976	$123.30	$123.30	$123.30
Purchase #7	$211.60	5.248%	$222.7048	$222.70	$222.70	$222.70
7 purchase totals =	$1,025.16		$1,108.2844	$1,108.28	$1,108.25	$1,108.40