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	$184.90	4.213%	$192.6898	$192.69	$192.70	$192.70
Purchase #2	$114.26	11.788%	$127.729	$127.73	$127.75	$127.70
Purchase #3	$85.52	5.175%	$89.9457	$89.95	$89.95	$89.90
Purchase #4	$76.88	9.389%	$84.0983	$84.10	$84.10	$84.10
Purchase #5	$235.39	4.149%	$245.1563	$245.16	$245.15	$245.20
Purchase #6	$32.43	12.807%	$36.5833	$36.58	$36.60	$36.60
Purchase #7	$158.44	6.241%	$168.3282	$168.33	$168.35	$168.30
7 purchase totals =	$887.82		$944.5306	$944.54	$944.60	$944.50