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	$198.50	13.486%	$225.2697	$225.27	$225.25	$225.30
Purchase #2	$106.42	5.411%	$112.1784	$112.18	$112.20	$112.20
Purchase #3	$18.83	5.245%	$19.8176	$19.82	$19.80	$19.80
Purchase #4	$154.38	13.269%	$174.8647	$174.86	$174.85	$174.90
Purchase #5	$103.38	9.814%	$113.5257	$113.53	$113.55	$113.50
Purchase #6	$224.42	13.806%	$255.4034	$255.40	$255.40	$255.40
Purchase #7	$87.69	13.200%	$99.2651	$99.27	$99.25	$99.30
7 purchase totals =	$893.62		$1,000.3246	$1,000.33	$1,000.30	$1,000.40