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	$132.66	7.740%	$142.9279	$142.93	$142.95	$142.90
Purchase #2	$99.52	8.799%	$108.2768	$108.28	$108.30	$108.30
Purchase #3	$19.63	4.758%	$20.564	$20.56	$20.55	$20.60
Purchase #4	$100.61	9.871%	$110.5412	$110.54	$110.55	$110.50
Purchase #5	$32.52	12.524%	$36.5928	$36.59	$36.60	$36.60
Purchase #6	$129.86	5.736%	$137.3088	$137.31	$137.30	$137.30
Purchase #7	$98.77	10.794%	$109.4312	$109.43	$109.45	$109.40
7 purchase totals =	$613.57		$665.6427	$665.64	$665.70	$665.60