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	$186.26	7.344%	$199.9389	$199.94	$199.95	$199.90
Purchase #2	$134.73	11.735%	$150.5406	$150.54	$150.55	$150.50
Purchase #3	$151.96	6.815%	$162.3161	$162.32	$162.30	$162.30
Purchase #4	$86.96	6.280%	$92.4211	$92.42	$92.40	$92.40
Purchase #5	$83.49	3.715%	$86.5917	$86.59	$86.60	$86.60
Purchase #6	$174.64	4.627%	$182.7206	$182.72	$182.70	$182.70
Purchase #7	$67.28	4.636%	$70.3991	$70.40	$70.40	$70.40
7 purchase totals =	$885.32		$944.9281	$944.93	$944.90	$944.80