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	$174.64	13.722%	$198.6041	$198.60	$198.60	$198.60
Purchase #2	$198.81	7.538%	$213.7963	$213.80	$213.80	$213.80
Purchase #3	$235.48	13.430%	$267.105	$267.11	$267.10	$267.10
Purchase #4	$183.63	4.224%	$191.3865	$191.39	$191.40	$191.40
Purchase #5	$53.73	10.421%	$59.3292	$59.33	$59.35	$59.30
Purchase #6	$122.43	7.348%	$131.4262	$131.43	$131.45	$131.40
Purchase #7	$144.76	6.607%	$154.3243	$154.32	$154.30	$154.30
7 purchase totals =	$1,113.48		$1,215.9716	$1,215.98	$1,216.00	$1,215.90