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	$54.47	8.167%	$58.9186	$58.92	$58.90	$58.90
Purchase #2	$175.69	7.833%	$189.4518	$189.45	$189.45	$189.50
Purchase #3	$215.29	13.571%	$244.507	$244.51	$244.50	$244.50
Purchase #4	$94.83	8.678%	$103.0593	$103.06	$103.05	$103.10
Purchase #5	$72.94	12.771%	$82.2552	$82.26	$82.25	$82.30
Purchase #6	$171.41	5.257%	$180.421	$180.42	$180.40	$180.40
Purchase #7	$185.66	8.746%	$201.8978	$201.90	$201.90	$201.90
7 purchase totals =	$970.29		$1,060.5107	$1,060.52	$1,060.45	$1,060.60