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	$200.95	5.254%	$211.5079	$211.51	$211.50	$211.50
Purchase #2	$33.84	3.780%	$35.1192	$35.12	$35.10	$35.10
Purchase #3	$99.85	5.275%	$105.1171	$105.12	$105.10	$105.10
Purchase #4	$21.58	6.150%	$22.9072	$22.91	$22.90	$22.90
Purchase #5	$146.44	13.650%	$166.4291	$166.43	$166.45	$166.40
Purchase #6	$167.60	11.307%	$186.5505	$186.55	$186.55	$186.60
Purchase #7	$243.62	5.229%	$256.3589	$256.36	$256.35	$256.40
7 purchase totals =	$913.88		$983.9899	$984.00	$983.95	$984.00