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	$186.25	7.300%	$199.8463	$199.85	$199.85	$199.80
Purchase #2	$247.32	13.517%	$280.7502	$280.75	$280.75	$280.80
Purchase #3	$235.64	3.198%	$243.1758	$243.18	$243.20	$243.20
Purchase #4	$94.85	11.232%	$105.5036	$105.50	$105.50	$105.50
Purchase #5	$211.77	6.857%	$226.2911	$226.29	$226.30	$226.30
Purchase #6	$129.75	9.644%	$142.2631	$142.26	$142.25	$142.30
Purchase #7	$32.46	4.300%	$33.8558	$33.86	$33.85	$33.90
7 purchase totals =	$1,138.04		$1,231.6859	$1,231.69	$1,231.70	$1,231.80