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	$69.76	8.356%	$75.5891	$75.59	$75.60	$75.60
Purchase #2	$147.25	11.745%	$164.5445	$164.54	$164.55	$164.50
Purchase #3	$226.45	7.423%	$243.2594	$243.26	$243.25	$243.30
Purchase #4	$175.45	13.542%	$199.2094	$199.21	$199.20	$199.20
Purchase #5	$56.48	10.346%	$62.3234	$62.32	$62.30	$62.30
Purchase #6	$88.48	13.322%	$100.2673	$100.27	$100.25	$100.30
Purchase #7	$248.39	6.587%	$264.7514	$264.75	$264.75	$264.80
7 purchase totals =	$1,012.26		$1,109.9445	$1,109.94	$1,109.90	$1,110.00