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	$131.41	13.592%	$149.2712	$149.27	$149.25	$149.30
Purchase #2	$219.98	5.113%	$231.2276	$231.23	$231.25	$231.20
Purchase #3	$62.76	7.566%	$67.5084	$67.51	$67.50	$67.50
Purchase #4	$135.74	6.319%	$144.3174	$144.32	$144.30	$144.30
Purchase #5	$42.97	12.564%	$48.3688	$48.37	$48.35	$48.40
Purchase #6	$241.86	11.462%	$269.582	$269.58	$269.60	$269.60
Purchase #7	$236.77	10.480%	$261.5835	$261.58	$261.60	$261.60
7 purchase totals =	$1,071.49		$1,171.8589	$1,171.86	$1,171.85	$1,171.90