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	$89.61	11.116%	$99.571	$99.57	$99.55	$99.60
Purchase #2	$29.60	11.622%	$33.0401	$33.04	$33.05	$33.00
Purchase #3	$187.72	3.564%	$194.4103	$194.41	$194.40	$194.40
Purchase #4	$177.62	7.631%	$191.1742	$191.17	$191.15	$191.20
Purchase #5	$45.77	13.652%	$52.0185	$52.02	$52.00	$52.00
Purchase #6	$6.28	12.731%	$7.0795	$7.08	$7.10	$7.10
Purchase #7	$110.86	5.761%	$117.2466	$117.25	$117.25	$117.20
7 purchase totals =	$647.46		$694.5402	$694.54	$694.50	$694.50