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	$174.82	12.275%	$196.2792	$196.28	$196.30	$196.30
Purchase #2	$131.65	8.472%	$142.8034	$142.80	$142.80	$142.80
Purchase #3	$114.29	3.370%	$118.1416	$118.14	$118.15	$118.10
Purchase #4	$195.86	13.801%	$222.8906	$222.89	$222.90	$222.90
Purchase #5	$145.66	8.661%	$158.2756	$158.28	$158.30	$158.30
Purchase #6	$52.86	7.380%	$56.7611	$56.76	$56.75	$56.80
Purchase #7	$61.70	9.246%	$67.4048	$67.40	$67.40	$67.40
7 purchase totals =	$876.84		$962.5563	$962.55	$962.60	$962.60