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	$194.47	4.792%	$203.789	$203.79	$203.80	$203.80
Purchase #2	$81.65	9.428%	$89.348	$89.35	$89.35	$89.30
Purchase #3	$233.79	4.836%	$245.0961	$245.10	$245.10	$245.10
Purchase #4	$245.56	9.299%	$268.3946	$268.39	$268.40	$268.40
Purchase #5	$101.92	4.632%	$106.6409	$106.64	$106.65	$106.60
Purchase #6	$104.38	5.187%	$109.7942	$109.79	$109.80	$109.80
Purchase #7	$18.51	11.249%	$20.5922	$20.59	$20.60	$20.60
7 purchase totals =	$980.28		$1,043.6550	$1,043.65	$1,043.70	$1,043.60