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	$168.41	13.609%	$191.3289	$191.33	$191.35	$191.30
Purchase #2	$163.52	5.550%	$172.5954	$172.60	$172.60	$172.60
Purchase #3	$127.41	9.628%	$139.677	$139.68	$139.70	$139.70
Purchase #4	$11.48	6.521%	$12.2286	$12.23	$12.25	$12.20
Purchase #5	$199.38	6.166%	$211.6738	$211.67	$211.65	$211.70
Purchase #6	$77.86	3.301%	$80.4302	$80.43	$80.45	$80.40
Purchase #7	$130.64	4.535%	$136.5645	$136.56	$136.55	$136.60
7 purchase totals =	$878.70		$944.4984	$944.50	$944.55	$944.50