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	$203.32	10.475%	$224.6178	$224.62	$224.60	$224.60
Purchase #2	$110.99	13.102%	$125.5319	$125.53	$125.55	$125.50
Purchase #3	$115.58	13.489%	$131.1706	$131.17	$131.15	$131.20
Purchase #4	$142.53	9.639%	$156.2685	$156.27	$156.25	$156.30
Purchase #5	$145.46	4.543%	$152.0682	$152.07	$152.05	$152.10
Purchase #6	$89.37	8.472%	$96.9414	$96.94	$96.95	$96.90
Purchase #7	$154.58	11.414%	$172.2238	$172.22	$172.20	$172.20
7 purchase totals =	$961.83		$1,058.8222	$1,058.82	$1,058.75	$1,058.80