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	$216.96	12.265%	$243.5701	$243.57	$243.55	$243.60
Purchase #2	$46.89	9.751%	$51.4622	$51.46	$51.45	$51.50
Purchase #3	$31.84	3.288%	$32.8869	$32.89	$32.90	$32.90
Purchase #4	$171.69	8.772%	$186.7506	$186.75	$186.75	$186.80
Purchase #5	$61.31	8.154%	$66.3092	$66.31	$66.30	$66.30
Purchase #6	$152.33	4.377%	$158.9975	$159.00	$159.00	$159.00
Purchase #7	$236.33	3.191%	$243.8713	$243.87	$243.85	$243.90
7 purchase totals =	$917.35		$983.8478	$983.85	$983.80	$984.00