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	$189.47	5.818%	$200.4934	$200.49	$200.50	$200.50
Purchase #2	$190.39	11.153%	$211.6242	$211.62	$211.60	$211.60
Purchase #3	$62.49	11.759%	$69.8382	$69.84	$69.85	$69.80
Purchase #4	$198.59	6.804%	$212.1021	$212.10	$212.10	$212.10
Purchase #5	$120.85	13.322%	$136.9496	$136.95	$136.95	$136.90
Purchase #6	$144.33	5.541%	$152.3273	$152.33	$152.35	$152.30
Purchase #7	$34.34	5.692%	$36.2946	$36.29	$36.30	$36.30
7 purchase totals =	$940.46		$1,019.6294	$1,019.62	$1,019.65	$1,019.50