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	$68.95	13.603%	$78.3293	$78.33	$78.35	$78.30
Purchase #2	$42.74	3.121%	$44.0739	$44.07	$44.05	$44.10
Purchase #3	$73.74	12.407%	$82.8889	$82.89	$82.90	$82.90
Purchase #4	$156.85	13.829%	$178.5408	$178.54	$178.55	$178.50
Purchase #5	$187.87	5.485%	$198.1747	$198.17	$198.15	$198.20
Purchase #6	$130.96	7.301%	$140.5214	$140.52	$140.50	$140.50
Purchase #7	$169.59	11.763%	$189.5389	$189.54	$189.55	$189.50
7 purchase totals =	$830.70		$912.0679	$912.06	$912.05	$912.00