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	$82.97	11.280%	$92.329	$92.33	$92.35	$92.30
Purchase #2	$66.36	8.404%	$71.9369	$71.94	$71.95	$71.90
Purchase #3	$10.80	6.271%	$11.4773	$11.48	$11.50	$11.50
Purchase #4	$181.27	10.590%	$200.4665	$200.47	$200.45	$200.50
Purchase #5	$181.54	13.399%	$205.8645	$205.86	$205.85	$205.90
Purchase #6	$165.31	10.359%	$182.4345	$182.43	$182.45	$182.40
Purchase #7	$148.53	7.689%	$159.9505	$159.95	$159.95	$160.00
7 purchase totals =	$836.78		$924.4592	$924.46	$924.50	$924.50