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	$139.81	7.625%	$150.4705	$150.47	$150.45	$150.50
Purchase #2	$18.35	11.607%	$20.4799	$20.48	$20.50	$20.50
Purchase #3	$73.46	10.425%	$81.1182	$81.12	$81.10	$81.10
Purchase #4	$118.65	4.137%	$123.5586	$123.56	$123.55	$123.60
Purchase #5	$104.67	10.110%	$115.2521	$115.25	$115.25	$115.30
Purchase #6	$63.52	4.383%	$66.3041	$66.30	$66.30	$66.30
Purchase #7	$116.32	11.418%	$129.6014	$129.60	$129.60	$129.60
7 purchase totals =	$634.78		$686.7848	$686.78	$686.75	$686.90