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	$235.51	5.310%	$248.0156	$248.02	$248.00	$248.00
Purchase #2	$69.91	11.260%	$77.7819	$77.78	$77.80	$77.80
Purchase #3	$99.31	10.690%	$109.9262	$109.93	$109.95	$109.90
Purchase #4	$198.98	4.768%	$208.4674	$208.47	$208.45	$208.50
Purchase #5	$167.42	4.250%	$174.5354	$174.54	$174.55	$174.50
Purchase #6	$129.25	6.550%	$137.7159	$137.72	$137.70	$137.70
Purchase #7	$88.34	11.694%	$98.6705	$98.67	$98.65	$98.70
7 purchase totals =	$988.72		$1,055.1129	$1,055.13	$1,055.10	$1,055.10