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	$165.37	5.557%	$174.5596	$174.56	$174.55	$174.60
Purchase #2	$193.27	10.759%	$214.0639	$214.06	$214.05	$214.10
Purchase #3	$246.93	9.373%	$270.0747	$270.07	$270.05	$270.10
Purchase #4	$86.65	3.664%	$89.8249	$89.82	$89.80	$89.80
Purchase #5	$163.94	13.224%	$185.6194	$185.62	$185.60	$185.60
Purchase #6	$241.98	5.389%	$255.0203	$255.02	$255.00	$255.00
Purchase #7	$200.37	5.762%	$211.9153	$211.92	$211.90	$211.90
7 purchase totals =	$1,298.51		$1,401.0781	$1,401.07	$1,400.95	$1,401.10