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	$24.74	4.636%	$25.8869	$25.89	$25.90	$25.90
Purchase #2	$162.87	13.344%	$184.6034	$184.60	$184.60	$184.60
Purchase #3	$99.27	10.226%	$109.4214	$109.42	$109.40	$109.40
Purchase #4	$190.89	10.534%	$210.9984	$211.00	$211.00	$211.00
Purchase #5	$150.50	12.279%	$168.9799	$168.98	$169.00	$169.00
Purchase #6	$61.98	5.432%	$65.3468	$65.35	$65.35	$65.30
Purchase #7	$174.61	3.289%	$180.3529	$180.35	$180.35	$180.40
7 purchase totals =	$864.86		$945.5897	$945.59	$945.60	$945.60