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	$165.28	3.454%	$170.9888	$170.99	$171.00	$171.00
Purchase #2	$25.89	9.807%	$28.429	$28.43	$28.45	$28.40
Purchase #3	$198.31	12.221%	$222.5455	$222.55	$222.55	$222.50
Purchase #4	$122.46	3.854%	$127.1796	$127.18	$127.20	$127.20
Purchase #5	$98.36	6.516%	$104.7691	$104.77	$104.75	$104.80
Purchase #6	$223.36	11.216%	$248.4121	$248.41	$248.40	$248.40
Purchase #7	$148.96	6.273%	$158.3043	$158.30	$158.30	$158.30
7 purchase totals =	$982.62		$1,060.6284	$1,060.63	$1,060.65	$1,060.60