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	$125.93	13.332%	$142.719	$142.72	$142.70	$142.70
Purchase #2	$103.74	8.731%	$112.7975	$112.80	$112.80	$112.80
Purchase #3	$78.27	3.566%	$81.0611	$81.06	$81.05	$81.10
Purchase #4	$72.50	13.430%	$82.2368	$82.24	$82.25	$82.20
Purchase #5	$80.37	5.865%	$85.0837	$85.08	$85.10	$85.10
Purchase #6	$93.46	6.266%	$99.3162	$99.32	$99.30	$99.30
Purchase #7	$21.91	6.715%	$23.3813	$23.38	$23.40	$23.40
7 purchase totals =	$576.18		$626.5956	$626.60	$626.60	$626.60