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	$148.87	13.234%	$168.5715	$168.57	$168.55	$168.60
Purchase #2	$163.86	9.307%	$179.1105	$179.11	$179.10	$179.10
Purchase #3	$185.65	6.839%	$198.3466	$198.35	$198.35	$198.30
Purchase #4	$90.78	5.142%	$95.4479	$95.45	$95.45	$95.40
Purchase #5	$40.31	13.703%	$45.8337	$45.83	$45.85	$45.80
Purchase #6	$89.80	7.751%	$96.7604	$96.76	$96.75	$96.80
Purchase #7	$124.76	8.570%	$135.4519	$135.45	$135.45	$135.50
7 purchase totals =	$844.03		$919.5225	$919.52	$919.50	$919.50