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	$37.86	10.291%	$41.7562	$41.76	$41.75	$41.80
Purchase #2	$72.93	7.757%	$78.5872	$78.59	$78.60	$78.60
Purchase #3	$134.99	10.420%	$149.056	$149.06	$149.05	$149.10
Purchase #4	$160.40	9.453%	$175.5626	$175.56	$175.55	$175.60
Purchase #5	$50.57	9.392%	$55.3195	$55.32	$55.30	$55.30
Purchase #6	$90.55	7.794%	$97.6075	$97.61	$97.60	$97.60
Purchase #7	$181.28	10.388%	$200.1114	$200.11	$200.10	$200.10
7 purchase totals =	$728.58		$798.0004	$798.01	$797.95	$798.10