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	$225.42	9.816%	$247.5472	$247.55	$247.55	$247.50
Purchase #2	$148.73	6.220%	$157.981	$157.98	$158.00	$158.00
Purchase #3	$89.89	10.383%	$99.2233	$99.22	$99.20	$99.20
Purchase #4	$248.30	7.236%	$266.267	$266.27	$266.25	$266.30
Purchase #5	$114.59	11.496%	$127.7633	$127.76	$127.75	$127.80
Purchase #6	$175.78	13.161%	$198.9144	$198.91	$198.90	$198.90
Purchase #7	$79.65	7.180%	$85.3689	$85.37	$85.35	$85.40
7 purchase totals =	$1,082.36		$1,183.0651	$1,183.06	$1,183.00	$1,183.10