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	$55.88	11.685%	$62.4096	$62.41	$62.40	$62.40
Purchase #2	$89.91	10.135%	$99.0224	$99.02	$99.00	$99.00
Purchase #3	$131.52	5.180%	$138.3327	$138.33	$138.35	$138.30
Purchase #4	$172.84	5.585%	$182.4931	$182.49	$182.50	$182.50
Purchase #5	$178.26	10.278%	$196.5816	$196.58	$196.60	$196.60
Purchase #6	$18.26	11.349%	$20.3323	$20.33	$20.35	$20.30
Purchase #7	$9.43	13.847%	$10.7358	$10.74	$10.75	$10.70
7 purchase totals =	$656.10		$709.9075	$709.90	$709.95	$709.80