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	$92.48	3.871%	$96.0599	$96.06	$96.05	$96.10
Purchase #2	$94.27	3.590%	$97.6543	$97.65	$97.65	$97.70
Purchase #3	$37.73	3.738%	$39.1403	$39.14	$39.15	$39.10
Purchase #4	$156.93	6.612%	$167.3062	$167.31	$167.30	$167.30
Purchase #5	$95.77	10.215%	$105.5529	$105.55	$105.55	$105.60
Purchase #6	$45.26	7.355%	$48.5889	$48.59	$48.60	$48.60
Purchase #7	$124.94	11.725%	$139.5892	$139.59	$139.60	$139.60
7 purchase totals =	$647.38		$693.8917	$693.89	$693.90	$694.00