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	$188.57	6.519%	$200.8629	$200.86	$200.85	$200.90
Purchase #2	$174.83	10.360%	$192.9424	$192.94	$192.95	$192.90
Purchase #3	$138.73	6.604%	$147.8917	$147.89	$147.90	$147.90
Purchase #4	$129.54	9.355%	$141.6585	$141.66	$141.65	$141.70
Purchase #5	$115.59	7.406%	$124.1506	$124.15	$124.15	$124.20
Purchase #6	$78.80	9.618%	$86.379	$86.38	$86.40	$86.40
Purchase #7	$230.64	10.611%	$255.1132	$255.11	$255.10	$255.10
7 purchase totals =	$1,056.70		$1,148.9983	$1,148.99	$1,149.00	$1,149.10