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	$189.58	11.543%	$211.4632	$211.46	$211.45	$211.50
Purchase #2	$105.38	10.515%	$116.4607	$116.46	$116.45	$116.50
Purchase #3	$76.70	6.312%	$81.5413	$81.54	$81.55	$81.50
Purchase #4	$98.33	12.686%	$110.8041	$110.80	$110.80	$110.80
Purchase #5	$177.77	3.683%	$184.3173	$184.32	$184.30	$184.30
Purchase #6	$160.52	3.688%	$166.44	$166.44	$166.45	$166.40
Purchase #7	$32.89	13.744%	$37.4104	$37.41	$37.40	$37.40
7 purchase totals =	$841.17		$908.4370	$908.43	$908.40	$908.40