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	$33.79	4.865%	$35.4339	$35.43	$35.45	$35.40
Purchase #2	$218.93	6.184%	$232.4686	$232.47	$232.45	$232.50
Purchase #3	$127.66	9.289%	$139.5183	$139.52	$139.50	$139.50
Purchase #4	$220.48	13.173%	$249.5238	$249.52	$249.50	$249.50
Purchase #5	$69.89	11.682%	$78.0545	$78.05	$78.05	$78.10
Purchase #6	$219.69	11.119%	$244.1173	$244.12	$244.10	$244.10
Purchase #7	$97.83	12.424%	$109.9844	$109.98	$110.00	$110.00
7 purchase totals =	$988.27		$1,089.1008	$1,089.09	$1,089.05	$1,089.10