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	$88.78	8.571%	$96.3893	$96.39	$96.40	$96.40
Purchase #2	$102.45	11.804%	$114.5432	$114.54	$114.55	$114.50
Purchase #3	$34.48	11.351%	$38.3938	$38.39	$38.40	$38.40
Purchase #4	$85.52	4.700%	$89.5394	$89.54	$89.55	$89.50
Purchase #5	$147.77	7.843%	$159.3596	$159.36	$159.35	$159.40
Purchase #6	$162.79	9.641%	$178.4846	$178.48	$178.50	$178.50
Purchase #7	$192.70	8.699%	$209.463	$209.46	$209.45	$209.50
7 purchase totals =	$814.49		$886.1729	$886.16	$886.20	$886.20