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	$188.61	11.831%	$210.9244	$210.92	$210.90	$210.90
Purchase #2	$13.64	5.397%	$14.3762	$14.38	$14.40	$14.40
Purchase #3	$29.27	12.165%	$32.8307	$32.83	$32.85	$32.80
Purchase #4	$157.50	9.751%	$172.8578	$172.86	$172.85	$172.90
Purchase #5	$237.32	10.710%	$262.737	$262.74	$262.75	$262.70
Purchase #6	$228.52	13.176%	$258.6298	$258.63	$258.65	$258.60
Purchase #7	$211.93	4.630%	$221.7424	$221.74	$221.75	$221.70
7 purchase totals =	$1,066.79		$1,174.0983	$1,174.10	$1,174.15	$1,174.00