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	$218.52	4.142%	$227.5711	$227.57	$227.55	$227.60
Purchase #2	$78.48	5.402%	$82.7195	$82.72	$82.70	$82.70
Purchase #3	$132.55	3.251%	$136.8592	$136.86	$136.85	$136.90
Purchase #4	$47.57	9.337%	$52.0116	$52.01	$52.00	$52.00
Purchase #5	$110.52	9.459%	$120.9741	$120.97	$120.95	$121.00
Purchase #6	$162.81	11.413%	$181.3915	$181.39	$181.40	$181.40
Purchase #7	$90.39	9.485%	$98.9635	$98.96	$98.95	$99.00
7 purchase totals =	$840.84		$900.4905	$900.48	$900.40	$900.60