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	$54.89	11.361%	$61.1261	$61.13	$61.15	$61.10
Purchase #2	$24.61	12.661%	$27.7259	$27.73	$27.75	$27.70
Purchase #3	$228.41	10.713%	$252.8796	$252.88	$252.90	$252.90
Purchase #4	$127.31	11.319%	$141.7202	$141.72	$141.70	$141.70
Purchase #5	$241.88	9.228%	$264.2007	$264.20	$264.20	$264.20
Purchase #6	$202.27	10.520%	$223.5488	$223.55	$223.55	$223.50
Purchase #7	$216.28	12.723%	$243.7973	$243.80	$243.80	$243.80
7 purchase totals =	$1,095.65		$1,214.9986	$1,215.01	$1,215.05	$1,214.90