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	$122.27	5.121%	$128.5314	$128.53	$128.55	$128.50
Purchase #2	$176.44	11.354%	$196.473	$196.47	$196.45	$196.50
Purchase #3	$129.38	11.337%	$144.0478	$144.05	$144.05	$144.00
Purchase #4	$164.78	6.362%	$175.2633	$175.26	$175.25	$175.30
Purchase #5	$99.30	11.154%	$110.3759	$110.38	$110.40	$110.40
Purchase #6	$183.28	5.742%	$193.8039	$193.80	$193.80	$193.80
Purchase #7	$91.88	10.266%	$101.3124	$101.31	$101.30	$101.30
7 purchase totals =	$967.33		$1,049.8077	$1,049.80	$1,049.80	$1,049.80