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	$250.85	7.479%	$269.6111	$269.61	$269.60	$269.60
Purchase #2	$134.66	7.535%	$144.8066	$144.81	$144.80	$144.80
Purchase #3	$6.77	6.807%	$7.2308	$7.23	$7.25	$7.20
Purchase #4	$78.97	9.242%	$86.2684	$86.27	$86.25	$86.30
Purchase #5	$55.38	7.318%	$59.4327	$59.43	$59.45	$59.40
Purchase #6	$28.36	12.673%	$31.9541	$31.95	$31.95	$32.00
Purchase #7	$188.88	9.730%	$207.258	$207.26	$207.25	$207.30
7 purchase totals =	$743.87		$806.5617	$806.56	$806.55	$806.60