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	$112.57	11.328%	$125.3219	$125.32	$125.30	$125.30
Purchase #2	$96.72	10.597%	$106.9694	$106.97	$106.95	$107.00
Purchase #3	$27.91	6.224%	$29.6471	$29.65	$29.65	$29.60
Purchase #4	$130.40	5.493%	$137.5629	$137.56	$137.55	$137.60
Purchase #5	$42.78	7.488%	$45.9834	$45.98	$46.00	$46.00
Purchase #6	$115.63	3.151%	$119.2735	$119.27	$119.25	$119.30
Purchase #7	$172.80	13.479%	$196.0917	$196.09	$196.10	$196.10
7 purchase totals =	$698.81		$760.8499	$760.84	$760.80	$760.90