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	$203.50	4.142%	$211.929	$211.93	$211.95	$211.90
Purchase #2	$51.84	11.811%	$57.9628	$57.96	$57.95	$58.00
Purchase #3	$136.27	10.356%	$150.3821	$150.38	$150.40	$150.40
Purchase #4	$219.46	7.857%	$236.703	$236.70	$236.70	$236.70
Purchase #5	$167.93	4.460%	$175.4197	$175.42	$175.40	$175.40
Purchase #6	$39.78	6.380%	$42.318	$42.32	$42.30	$42.30
Purchase #7	$158.49	4.466%	$165.5682	$165.57	$165.55	$165.60
7 purchase totals =	$977.27		$1,040.2828	$1,040.28	$1,040.25	$1,040.30