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	$175.61	6.614%	$187.2248	$187.22	$187.20	$187.20
Purchase #2	$240.52	4.157%	$250.5184	$250.52	$250.50	$250.50
Purchase #3	$105.47	6.207%	$112.0165	$112.02	$112.00	$112.00
Purchase #4	$215.70	9.468%	$236.1225	$236.12	$236.10	$236.10
Purchase #5	$117.34	5.229%	$123.4757	$123.48	$123.50	$123.50
Purchase #6	$7.78	3.552%	$8.0563	$8.06	$8.05	$8.10
Purchase #7	$148.74	11.300%	$165.5476	$165.55	$165.55	$165.50
7 purchase totals =	$1,011.16		$1,082.9618	$1,082.97	$1,082.90	$1,082.90