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	$191.67	11.587%	$213.8788	$213.88	$213.90	$213.90
Purchase #2	$96.96	4.606%	$101.426	$101.43	$101.45	$101.40
Purchase #3	$76.30	13.779%	$86.8134	$86.81	$86.80	$86.80
Purchase #4	$171.90	7.535%	$184.8527	$184.85	$184.85	$184.90
Purchase #5	$88.46	4.285%	$92.2505	$92.25	$92.25	$92.30
Purchase #6	$33.38	11.835%	$37.3305	$37.33	$37.35	$37.30
Purchase #7	$107.25	3.652%	$111.1668	$111.17	$111.15	$111.20
7 purchase totals =	$765.92		$827.7187	$827.72	$827.75	$827.80