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	$163.52	12.534%	$184.0156	$184.02	$184.00	$184.00
Purchase #2	$18.51	5.113%	$19.4564	$19.46	$19.45	$19.50
Purchase #3	$244.30	9.765%	$268.1559	$268.16	$268.15	$268.20
Purchase #4	$37.42	13.396%	$42.4328	$42.43	$42.45	$42.40
Purchase #5	$55.34	11.292%	$61.589	$61.59	$61.60	$61.60
Purchase #6	$234.97	9.459%	$257.1958	$257.20	$257.20	$257.20
Purchase #7	$249.83	7.124%	$267.6279	$267.63	$267.65	$267.60
7 purchase totals =	$1,003.89		$1,100.4734	$1,100.49	$1,100.50	$1,100.50