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	$89.64	11.148%	$99.6331	$99.63	$99.65	$99.60
Purchase #2	$185.75	5.666%	$196.2746	$196.27	$196.25	$196.30
Purchase #3	$97.51	5.284%	$102.6624	$102.66	$102.65	$102.70
Purchase #4	$84.88	11.186%	$94.3747	$94.37	$94.35	$94.40
Purchase #5	$206.62	9.183%	$225.5939	$225.59	$225.60	$225.60
Purchase #6	$17.54	10.841%	$19.4415	$19.44	$19.45	$19.40
Purchase #7	$58.31	5.205%	$61.345	$61.35	$61.35	$61.30
7 purchase totals =	$740.25		$799.3252	$799.31	$799.30	$799.30