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	$140.45	8.454%	$152.3236	$152.32	$152.30	$152.30
Purchase #2	$96.81	4.676%	$101.3368	$101.34	$101.35	$101.30
Purchase #3	$166.98	10.721%	$184.8819	$184.88	$184.90	$184.90
Purchase #4	$105.49	3.715%	$109.409	$109.41	$109.40	$109.40
Purchase #5	$84.91	6.182%	$90.1591	$90.16	$90.15	$90.20
Purchase #6	$128.88	3.138%	$132.9243	$132.92	$132.90	$132.90
Purchase #7	$234.63	9.297%	$256.4436	$256.44	$256.45	$256.40
7 purchase totals =	$958.15		$1,027.4783	$1,027.47	$1,027.45	$1,027.40