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	$41.99	6.112%	$44.5564	$44.56	$44.55	$44.60
Purchase #2	$80.73	9.132%	$88.1023	$88.10	$88.10	$88.10
Purchase #3	$89.67	6.768%	$95.7389	$95.74	$95.75	$95.70
Purchase #4	$109.82	13.254%	$124.3755	$124.38	$124.40	$124.40
Purchase #5	$34.82	6.419%	$37.0551	$37.06	$37.05	$37.10
Purchase #6	$63.47	4.112%	$66.0799	$66.08	$66.10	$66.10
Purchase #7	$190.36	11.248%	$211.7717	$211.77	$211.75	$211.80
7 purchase totals =	$610.86		$667.6798	$667.69	$667.70	$667.80