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	$211.46	5.340%	$222.752	$222.75	$222.75	$222.80
Purchase #2	$61.33	3.655%	$63.5716	$63.57	$63.55	$63.60
Purchase #3	$136.90	10.221%	$150.8925	$150.89	$150.90	$150.90
Purchase #4	$23.26	8.779%	$25.302	$25.30	$25.30	$25.30
Purchase #5	$65.38	3.124%	$67.4225	$67.42	$67.40	$67.40
Purchase #6	$223.38	10.763%	$247.4224	$247.42	$247.40	$247.40
Purchase #7	$11.42	5.195%	$12.0133	$12.01	$12.00	$12.00
7 purchase totals =	$733.13		$789.3763	$789.36	$789.30	$789.40