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	$97.45	4.616%	$101.9483	$101.95	$101.95	$101.90
Purchase #2	$89.91	4.181%	$93.6691	$93.67	$93.65	$93.70
Purchase #3	$164.26	3.118%	$169.3816	$169.38	$169.40	$169.40
Purchase #4	$189.67	3.756%	$196.794	$196.79	$196.80	$196.80
Purchase #5	$147.48	13.423%	$167.2762	$167.28	$167.30	$167.30
Purchase #6	$46.33	9.195%	$50.59	$50.59	$50.60	$50.60
Purchase #7	$82.78	10.177%	$91.2045	$91.20	$91.20	$91.20
7 purchase totals =	$817.88		$870.8637	$870.86	$870.90	$870.90