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	$59.98	9.328%	$65.5749	$65.57	$65.55	$65.60
Purchase #2	$168.62	9.728%	$185.0234	$185.02	$185.00	$185.00
Purchase #3	$167.87	9.505%	$183.826	$183.83	$183.85	$183.80
Purchase #4	$232.95	5.429%	$245.5969	$245.60	$245.60	$245.60
Purchase #5	$154.89	7.348%	$166.2713	$166.27	$166.25	$166.30
Purchase #6	$230.34	11.466%	$256.7508	$256.75	$256.75	$256.80
Purchase #7	$123.61	6.479%	$131.6187	$131.62	$131.60	$131.60
7 purchase totals =	$1,138.26		$1,234.6620	$1,234.66	$1,234.60	$1,234.70