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	$165.97	3.352%	$171.5333	$171.53	$171.55	$171.50
Purchase #2	$19.80	13.457%	$22.4645	$22.46	$22.45	$22.50
Purchase #3	$66.70	11.383%	$74.2925	$74.29	$74.30	$74.30
Purchase #4	$128.81	13.122%	$145.7124	$145.71	$145.70	$145.70
Purchase #5	$164.86	12.123%	$184.846	$184.85	$184.85	$184.80
Purchase #6	$23.78	6.292%	$25.2762	$25.28	$25.30	$25.30
Purchase #7	$40.52	7.673%	$43.6291	$43.63	$43.65	$43.60
7 purchase totals =	$610.44		$667.7540	$667.75	$667.80	$667.70