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	$157.33	4.869%	$164.9904	$164.99	$165.00	$165.00
Purchase #2	$159.45	3.478%	$164.9957	$165.00	$165.00	$165.00
Purchase #3	$35.67	12.446%	$40.1095	$40.11	$40.10	$40.10
Purchase #4	$160.65	13.478%	$182.3024	$182.30	$182.30	$182.30
Purchase #5	$83.46	9.620%	$91.4889	$91.49	$91.50	$91.50
Purchase #6	$30.82	8.346%	$33.3922	$33.39	$33.40	$33.40
Purchase #7	$156.69	7.839%	$168.9729	$168.97	$168.95	$169.00
7 purchase totals =	$784.07		$846.2520	$846.25	$846.25	$846.30