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	$208.41	6.309%	$221.5586	$221.56	$221.55	$221.60
Purchase #2	$233.88	5.636%	$247.0615	$247.06	$247.05	$247.10
Purchase #3	$54.83	11.278%	$61.0137	$61.01	$61.00	$61.00
Purchase #4	$118.67	7.686%	$127.791	$127.79	$127.80	$127.80
Purchase #5	$130.75	9.524%	$143.2026	$143.20	$143.20	$143.20
Purchase #6	$78.90	9.243%	$86.1927	$86.19	$86.20	$86.20
Purchase #7	$195.71	11.787%	$218.7783	$218.78	$218.80	$218.80
7 purchase totals =	$1,021.15		$1,105.5984	$1,105.59	$1,105.60	$1,105.70