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	$157.70	13.248%	$178.5921	$178.59	$178.60	$178.60
Purchase #2	$100.51	5.154%	$105.6903	$105.69	$105.70	$105.70
Purchase #3	$98.28	13.342%	$111.3925	$111.39	$111.40	$111.40
Purchase #4	$135.88	6.790%	$145.1063	$145.11	$145.10	$145.10
Purchase #5	$228.48	12.814%	$257.7574	$257.76	$257.75	$257.80
Purchase #6	$216.50	7.554%	$232.8544	$232.85	$232.85	$232.90
Purchase #7	$76.41	3.224%	$78.8735	$78.87	$78.85	$78.90
7 purchase totals =	$1,013.76		$1,110.2665	$1,110.26	$1,110.25	$1,110.40