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	$164.40	10.785%	$182.1305	$182.13	$182.15	$182.10
Purchase #2	$79.98	4.533%	$83.6055	$83.61	$83.60	$83.60
Purchase #3	$78.33	9.125%	$85.4776	$85.48	$85.50	$85.50
Purchase #4	$57.84	3.104%	$59.6354	$59.64	$59.65	$59.60
Purchase #5	$22.39	5.459%	$23.6123	$23.61	$23.60	$23.60
Purchase #6	$237.59	13.192%	$268.9329	$268.93	$268.95	$268.90
Purchase #7	$100.69	4.291%	$105.0106	$105.01	$105.00	$105.00
7 purchase totals =	$741.22		$808.4048	$808.41	$808.45	$808.30