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	$206.78	3.467%	$213.9491	$213.95	$213.95	$213.90
Purchase #2	$244.93	4.650%	$256.3192	$256.32	$256.30	$256.30
Purchase #3	$232.69	4.144%	$242.3327	$242.33	$242.35	$242.30
Purchase #4	$88.25	9.271%	$96.4317	$96.43	$96.45	$96.40
Purchase #5	$37.94	9.648%	$41.6005	$41.60	$41.60	$41.60
Purchase #6	$142.61	9.174%	$155.693	$155.69	$155.70	$155.70
Purchase #7	$164.61	12.391%	$185.0068	$185.01	$185.00	$185.00
7 purchase totals =	$1,117.81		$1,191.3330	$1,191.33	$1,191.35	$1,191.20