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	$221.30	9.322%	$241.9296	$241.93	$241.95	$241.90
Purchase #2	$70.28	12.311%	$78.9322	$78.93	$78.95	$78.90
Purchase #3	$160.70	13.422%	$182.2692	$182.27	$182.25	$182.30
Purchase #4	$84.32	6.742%	$90.0049	$90.00	$90.00	$90.00
Purchase #5	$64.28	5.821%	$68.0217	$68.02	$68.00	$68.00
Purchase #6	$247.52	3.490%	$256.1584	$256.16	$256.15	$256.20
Purchase #7	$98.34	5.626%	$103.8726	$103.87	$103.85	$103.90
7 purchase totals =	$946.74		$1,021.1886	$1,021.18	$1,021.15	$1,021.20