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	$147.50	3.349%	$152.4398	$152.44	$152.45	$152.40
Purchase #2	$172.93	4.700%	$181.0577	$181.06	$181.05	$181.10
Purchase #3	$230.90	3.315%	$238.5543	$238.55	$238.55	$238.60
Purchase #4	$158.33	9.582%	$173.5012	$173.50	$173.50	$173.50
Purchase #5	$140.46	7.774%	$151.3794	$151.38	$151.40	$151.40
Purchase #6	$206.75	7.259%	$221.758	$221.76	$221.75	$221.80
Purchase #7	$232.54	13.687%	$264.3677	$264.37	$264.35	$264.40
7 purchase totals =	$1,289.41		$1,383.0581	$1,383.06	$1,383.05	$1,383.20