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	$160.70	8.336%	$174.096	$174.10	$174.10	$174.10
Purchase #2	$109.27	13.155%	$123.6445	$123.64	$123.65	$123.60
Purchase #3	$133.91	5.561%	$141.3567	$141.36	$141.35	$141.40
Purchase #4	$161.86	4.589%	$169.2878	$169.29	$169.30	$169.30
Purchase #5	$172.97	3.869%	$179.6622	$179.66	$179.65	$179.70
Purchase #6	$162.75	3.219%	$167.9889	$167.99	$168.00	$168.00
Purchase #7	$131.27	4.713%	$137.4568	$137.46	$137.45	$137.50
7 purchase totals =	$1,032.73		$1,093.4929	$1,093.50	$1,093.50	$1,093.60