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	$205.73	8.639%	$223.503	$223.50	$223.50	$223.50
Purchase #2	$32.49	4.473%	$33.9433	$33.94	$33.95	$33.90
Purchase #3	$146.92	7.799%	$158.3783	$158.38	$158.40	$158.40
Purchase #4	$86.31	11.830%	$96.5205	$96.52	$96.50	$96.50
Purchase #5	$221.60	10.706%	$245.3245	$245.32	$245.30	$245.30
Purchase #6	$106.65	12.194%	$119.6549	$119.65	$119.65	$119.70
Purchase #7	$180.25	11.207%	$200.4506	$200.45	$200.45	$200.50
7 purchase totals =	$979.95		$1,077.7751	$1,077.76	$1,077.75	$1,077.80