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	$184.32	4.590%	$192.7803	$192.78	$192.80	$192.80
Purchase #2	$86.32	9.207%	$94.2675	$94.27	$94.25	$94.30
Purchase #3	$89.74	12.418%	$100.8839	$100.88	$100.90	$100.90
Purchase #4	$48.68	3.276%	$50.2748	$50.27	$50.25	$50.30
Purchase #5	$159.65	4.828%	$167.3579	$167.36	$167.35	$167.40
Purchase #6	$73.41	10.542%	$81.1489	$81.15	$81.15	$81.10
Purchase #7	$193.86	3.550%	$200.742	$200.74	$200.75	$200.70
7 purchase totals =	$835.98		$887.4553	$887.45	$887.45	$887.50