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	$162.70	13.481%	$184.6336	$184.63	$184.65	$184.60
Purchase #2	$183.97	9.189%	$200.875	$200.88	$200.90	$200.90
Purchase #3	$114.27	11.245%	$127.1197	$127.12	$127.10	$127.10
Purchase #4	$78.32	13.691%	$89.0428	$89.04	$89.05	$89.00
Purchase #5	$34.55	6.814%	$36.9042	$36.90	$36.90	$36.90
Purchase #6	$71.34	13.137%	$80.7119	$80.71	$80.70	$80.70
Purchase #7	$147.37	9.614%	$161.5382	$161.54	$161.55	$161.50
7 purchase totals =	$792.52		$880.8254	$880.82	$880.85	$880.70