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	$139.72	9.458%	$152.9347	$152.93	$152.95	$152.90
Purchase #2	$72.80	13.752%	$82.8115	$82.81	$82.80	$82.80
Purchase #3	$225.46	5.707%	$238.327	$238.33	$238.35	$238.30
Purchase #4	$105.60	3.470%	$109.2643	$109.26	$109.25	$109.30
Purchase #5	$150.78	6.844%	$161.0994	$161.10	$161.10	$161.10
Purchase #6	$106.52	10.143%	$117.3243	$117.32	$117.30	$117.30
Purchase #7	$244.44	9.593%	$267.8891	$267.89	$267.90	$267.90
7 purchase totals =	$1,045.32		$1,129.6503	$1,129.64	$1,129.65	$1,129.60