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	$54.29	12.458%	$61.0534	$61.05	$61.05	$61.10
Purchase #2	$136.94	11.640%	$152.8798	$152.88	$152.90	$152.90
Purchase #3	$167.39	8.292%	$181.27	$181.27	$181.25	$181.30
Purchase #4	$73.74	6.219%	$78.3259	$78.33	$78.35	$78.30
Purchase #5	$110.26	11.104%	$122.5033	$122.50	$122.50	$122.50
Purchase #6	$137.87	6.342%	$146.6137	$146.61	$146.60	$146.60
Purchase #7	$97.92	8.748%	$106.486	$106.49	$106.50	$106.50
7 purchase totals =	$778.41		$849.1321	$849.13	$849.15	$849.20