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	$85.69	13.626%	$97.3661	$97.37	$97.35	$97.40
Purchase #2	$119.64	10.251%	$131.9043	$131.90	$131.90	$131.90
Purchase #3	$88.33	9.631%	$96.8371	$96.84	$96.85	$96.80
Purchase #4	$30.69	5.525%	$32.3856	$32.39	$32.40	$32.40
Purchase #5	$105.32	4.735%	$110.3069	$110.31	$110.30	$110.30
Purchase #6	$152.26	6.866%	$162.7142	$162.71	$162.70	$162.70
Purchase #7	$87.40	3.440%	$90.4066	$90.41	$90.40	$90.40
7 purchase totals =	$669.33		$721.9208	$721.93	$721.90	$721.90