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	$182.71	7.435%	$196.2945	$196.29	$196.30	$196.30
Purchase #2	$25.66	5.743%	$27.1337	$27.13	$27.15	$27.10
Purchase #3	$50.27	8.334%	$54.4595	$54.46	$54.45	$54.50
Purchase #4	$99.59	4.798%	$104.3683	$104.37	$104.35	$104.40
Purchase #5	$199.54	8.114%	$215.7307	$215.73	$215.75	$215.70
Purchase #6	$79.60	10.584%	$88.0249	$88.02	$88.00	$88.00
Purchase #7	$114.92	6.289%	$122.1473	$122.15	$122.15	$122.10
7 purchase totals =	$752.29		$808.1589	$808.15	$808.15	$808.10