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	$146.38	10.655%	$161.9768	$161.98	$162.00	$162.00
Purchase #2	$188.81	13.873%	$215.0036	$215.00	$215.00	$215.00
Purchase #3	$101.53	7.505%	$109.1498	$109.15	$109.15	$109.10
Purchase #4	$90.58	9.787%	$99.4451	$99.45	$99.45	$99.40
Purchase #5	$83.35	10.213%	$91.8625	$91.86	$91.85	$91.90
Purchase #6	$27.35	11.245%	$30.4255	$30.43	$30.45	$30.40
Purchase #7	$134.67	6.552%	$143.4936	$143.49	$143.50	$143.50
7 purchase totals =	$772.67		$851.3569	$851.36	$851.40	$851.30