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	$52.31	13.745%	$59.5	$59.50	$59.50	$59.50
Purchase #2	$51.37	8.665%	$55.8212	$55.82	$55.80	$55.80
Purchase #3	$58.90	5.211%	$61.9693	$61.97	$61.95	$62.00
Purchase #4	$11.26	9.411%	$12.3197	$12.32	$12.30	$12.30
Purchase #5	$187.32	5.317%	$197.2798	$197.28	$197.30	$197.30
Purchase #6	$174.41	7.412%	$187.3373	$187.34	$187.35	$187.30
Purchase #7	$88.53	7.221%	$94.9228	$94.92	$94.90	$94.90
7 purchase totals =	$624.10		$669.1501	$669.15	$669.10	$669.10