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	$189.47	3.602%	$196.2947	$196.29	$196.30	$196.30
Purchase #2	$92.71	11.869%	$103.7137	$103.71	$103.70	$103.70
Purchase #3	$136.45	13.588%	$154.9908	$154.99	$155.00	$155.00
Purchase #4	$149.75	12.425%	$168.3564	$168.36	$168.35	$168.40
Purchase #5	$238.44	6.652%	$254.301	$254.30	$254.30	$254.30
Purchase #6	$171.28	10.656%	$189.5316	$189.53	$189.55	$189.50
Purchase #7	$19.87	10.167%	$21.8902	$21.89	$21.90	$21.90
7 purchase totals =	$997.97		$1,089.0784	$1,089.07	$1,089.10	$1,089.10