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	$95.42	8.417%	$103.4515	$103.45	$103.45	$103.50
Purchase #2	$215.82	3.335%	$223.0176	$223.02	$223.00	$223.00
Purchase #3	$219.42	3.613%	$227.3476	$227.35	$227.35	$227.30
Purchase #4	$14.81	9.867%	$16.2713	$16.27	$16.25	$16.30
Purchase #5	$167.36	7.307%	$179.589	$179.59	$179.60	$179.60
Purchase #6	$245.90	8.791%	$267.5171	$267.52	$267.50	$267.50
Purchase #7	$113.51	12.487%	$127.684	$127.68	$127.70	$127.70
7 purchase totals =	$1,072.24		$1,144.8781	$1,144.88	$1,144.85	$1,144.90