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	$105.27	3.312%	$108.7565	$108.76	$108.75	$108.80
Purchase #2	$69.54	13.452%	$78.8945	$78.89	$78.90	$78.90
Purchase #3	$205.92	7.776%	$221.9323	$221.93	$221.95	$221.90
Purchase #4	$227.28	11.866%	$254.249	$254.25	$254.25	$254.20
Purchase #5	$145.82	12.681%	$164.3114	$164.31	$164.30	$164.30
Purchase #6	$215.59	3.171%	$222.4264	$222.43	$222.45	$222.40
Purchase #7	$33.44	5.369%	$35.2354	$35.24	$35.25	$35.20
7 purchase totals =	$1,002.86		$1,085.8055	$1,085.81	$1,085.85	$1,085.70