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	$49.64	3.419%	$51.3372	$51.34	$51.35	$51.30
Purchase #2	$156.32	7.509%	$168.0581	$168.06	$168.05	$168.10
Purchase #3	$216.34	12.491%	$243.363	$243.36	$243.35	$243.40
Purchase #4	$62.55	4.556%	$65.3998	$65.40	$65.40	$65.40
Purchase #5	$120.25	9.167%	$131.2733	$131.27	$131.25	$131.30
Purchase #6	$102.50	6.665%	$109.3316	$109.33	$109.35	$109.30
Purchase #7	$95.53	10.325%	$105.3935	$105.39	$105.40	$105.40
7 purchase totals =	$803.13		$874.1565	$874.15	$874.15	$874.20