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	$105.68	5.698%	$111.7016	$111.70	$111.70	$111.70
Purchase #2	$67.65	7.545%	$72.7542	$72.75	$72.75	$72.80
Purchase #3	$144.58	7.304%	$155.1401	$155.14	$155.15	$155.10
Purchase #4	$61.43	6.337%	$65.3228	$65.32	$65.30	$65.30
Purchase #5	$161.56	4.132%	$168.2357	$168.24	$168.25	$168.20
Purchase #6	$157.64	13.303%	$178.6108	$178.61	$178.60	$178.60
Purchase #7	$107.33	4.674%	$112.3466	$112.35	$112.35	$112.30
7 purchase totals =	$805.87		$864.1118	$864.11	$864.10	$864.00