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	$236.87	8.802%	$257.7193	$257.72	$257.70	$257.70
Purchase #2	$178.56	7.199%	$191.4145	$191.41	$191.40	$191.40
Purchase #3	$92.63	4.110%	$96.4371	$96.44	$96.45	$96.40
Purchase #4	$72.79	7.746%	$78.4283	$78.43	$78.45	$78.40
Purchase #5	$83.88	8.202%	$90.7598	$90.76	$90.75	$90.80
Purchase #6	$159.50	4.837%	$167.215	$167.22	$167.20	$167.20
Purchase #7	$194.94	11.850%	$218.0404	$218.04	$218.05	$218.00
7 purchase totals =	$1,019.17		$1,100.0144	$1,100.02	$1,100.00	$1,099.90