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	$152.96	10.424%	$168.9046	$168.90	$168.90	$168.90
Purchase #2	$102.34	6.655%	$109.1507	$109.15	$109.15	$109.20
Purchase #3	$132.51	5.458%	$139.7424	$139.74	$139.75	$139.70
Purchase #4	$81.83	6.212%	$86.9133	$86.91	$86.90	$86.90
Purchase #5	$172.81	12.280%	$194.0311	$194.03	$194.05	$194.00
Purchase #6	$159.30	4.452%	$166.392	$166.39	$166.40	$166.40
Purchase #7	$233.54	4.614%	$244.3155	$244.32	$244.30	$244.30
7 purchase totals =	$1,035.29		$1,109.4496	$1,109.44	$1,109.45	$1,109.40