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	$176.69	13.254%	$200.1085	$200.11	$200.10	$200.10
Purchase #2	$156.77	11.488%	$174.7797	$174.78	$174.80	$174.80
Purchase #3	$79.55	12.502%	$89.4953	$89.50	$89.50	$89.50
Purchase #4	$36.61	5.794%	$38.7312	$38.73	$38.75	$38.70
Purchase #5	$124.67	13.469%	$141.4618	$141.46	$141.45	$141.50
Purchase #6	$242.27	6.260%	$257.4361	$257.44	$257.45	$257.40
Purchase #7	$6.47	3.119%	$6.6718	$6.67	$6.65	$6.70
7 purchase totals =	$823.03		$908.6844	$908.69	$908.70	$908.70