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	$45.32	5.171%	$47.6635	$47.66	$47.65	$47.70
Purchase #2	$124.92	3.168%	$128.8775	$128.88	$128.90	$128.90
Purchase #3	$134.86	11.508%	$150.3797	$150.38	$150.40	$150.40
Purchase #4	$246.41	5.342%	$259.5732	$259.57	$259.55	$259.60
Purchase #5	$205.73	7.590%	$221.3449	$221.34	$221.35	$221.30
Purchase #6	$137.90	11.556%	$153.8357	$153.84	$153.85	$153.80
Purchase #7	$47.77	13.636%	$54.2839	$54.28	$54.30	$54.30
7 purchase totals =	$942.91		$1,015.9584	$1,015.95	$1,016.00	$1,016.00