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	$64.96	10.816%	$71.9861	$71.99	$72.00	$72.00
Purchase #2	$79.76	13.497%	$90.5252	$90.53	$90.55	$90.50
Purchase #3	$155.72	11.629%	$173.8287	$173.83	$173.85	$173.80
Purchase #4	$243.59	11.842%	$272.4359	$272.44	$272.45	$272.40
Purchase #5	$115.52	12.823%	$130.3331	$130.33	$130.35	$130.30
Purchase #6	$6.86	4.474%	$7.1669	$7.17	$7.15	$7.20
Purchase #7	$45.97	11.694%	$51.3457	$51.35	$51.35	$51.30
7 purchase totals =	$712.38		$797.6216	$797.64	$797.70	$797.50