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	$172.69	13.651%	$196.2639	$196.26	$196.25	$196.30
Purchase #2	$95.93	6.799%	$102.4523	$102.45	$102.45	$102.50
Purchase #3	$24.43	13.191%	$27.6526	$27.65	$27.65	$27.70
Purchase #4	$134.27	6.434%	$142.9089	$142.91	$142.90	$142.90
Purchase #5	$99.75	4.789%	$104.527	$104.53	$104.55	$104.50
Purchase #6	$70.55	12.777%	$79.5642	$79.56	$79.55	$79.60
Purchase #7	$45.27	12.623%	$50.9844	$50.98	$51.00	$51.00
7 purchase totals =	$642.89		$704.3533	$704.34	$704.35	$704.50