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	$196.67	4.533%	$205.5851	$205.59	$205.60	$205.60
Purchase #2	$196.45	12.695%	$221.3893	$221.39	$221.40	$221.40
Purchase #3	$27.71	12.354%	$31.1333	$31.13	$31.15	$31.10
Purchase #4	$47.31	13.684%	$53.7839	$53.78	$53.80	$53.80
Purchase #5	$88.25	3.435%	$91.2814	$91.28	$91.30	$91.30
Purchase #6	$191.49	11.391%	$213.3026	$213.30	$213.30	$213.30
Purchase #7	$228.87	9.293%	$250.1389	$250.14	$250.15	$250.10
7 purchase totals =	$976.75		$1,066.6145	$1,066.61	$1,066.70	$1,066.60